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HOME  UNIVERSITY  LIBRARY 
OF  MODERN  KNOWLEDGE 

No.  14 

Editors : 

HERBERT    FISHER,  M.A.,  F.B.A. 
Prof.  GILBERT  MURRAY,  Litt.D., 

LL.D.,  F.B.A. 
Prof.  J.  ARTHUR    THOMSON,  M.A. 
Prof.  WILLIAM  T.  BREWSTER,  M.A, 


THE  HOME  UOTVEESITY  LIBRAEY 
OE  MODER]!T  K^^OWLEDGE 

i6mo  cloth,  50  cents  net,  by  mail  56  cents 

SCIENCE 

Already  Published 

ANTHROPOLOGY By  R.  R.  Marett 

AN    INTRODUCTION   TO 

SCIENCE By  J.  Arthur  Thomson 

EVOLUTION By  J.  Arthur  Thomson  and 

Patrick  Geddes 

THE  ANIMAL  WORLD By  F.  W.  Gamble 

INTRODUCTION     TO     MATHE- 
MATICS      By  A.  N.  Whitehead 

ASTRONOMY By  A.  R.  Hinks 

PSYCHICAL  RESEARCH   .    .    .    .  By  W.  F.  Barrett 
THE   EVOLUTION   OF   PLANTS  By  D.  H.  Scott 
CRIME   AND   INSANITY  ....  By  C.  A.  Mercier 
MATTER  AND   ENERGY  ....  By  F.  Soddy 

PSYCHOLOGY By  W.  McDougall 

PRINCIPLES    OF    PHYSIOLOGY  By  J.  G.  McKendhick 
THE  MAKING  OF  THE  EARTH  By  J.  W.  Gregory 

ELECTRICITY By  Gisbert  Kapp  f 

THE  HUMAN  BODY By  A.Kbith 

Future  Issues 

CHEMISTRY By  R.  Meldola 

THE  MINERAL  WORLD  ....  By  Sir  T.  H.  Holland 


EVOLUTION 

BY 

PATRICK    GEDDES 

11 

PROFESSOR    OF    BOTANY,    ST.    ANDREWS    UNIVERSITY 
^  AND 

jl  ARTHUR  THOMSON 

REGIUS    PROFESSOR    OF    NATURAL    HISTORY,    ABERDEEN 

UNIVERSITY 

Joint  Authors  of  "  The  E<volutton  of  SeXy^''  etc. 


NEW   YORK 
HENRY   HOLT   AND    COMPANY 

LONDON 
WILLIAMS   AND    NORGATE 


Copyright,  1911, 

BY 
HENRY    HOLT   AND    COMPANY 


THE  UNIVERSITY   PRESS,    CAMBRIDGE,   U.S.A. 


CONTENTS 

CHAP.  PAGE 

Introduction" vii 

I    Evidences  of  Evolution  from  Explorer  and 

Paleontologist 15 

II    Evidences    of     Evolution    from    Anatomist, 

Embryologist  and  Physiologist  ....  40 

III  Great  Steps  in  Evolution 67 

IV  Variation  and  Heredity 112 

V    Selection 143 

VI    Organism,  Function  and  Environment.     .     ,  183 

VII    Evolution  Theories  in  their   Social  Origins 

AND  Inter-Actions 212 

VIII    The  Evolution  Process  Once  More  Reinter- 
preted    233 

Bibliography 249 


Q^biA 


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INTRODUCTION 

Despite  the  many  and  wide  differences  so 
obvious  in  every  community — of  age  and  sex, 
of  regional  origins  and  historic  groupings,  of 
occupations  and  interests,  of  experience  and 
intelligence,  efficiency  and  originality,  of  edu- 
cation, manners  and  morals,  of  wealth  and 
rank,  and  so  on — each  generation  has  more 
in  common  than  its  individuals  may  realize. 
Layman  and  cleric,  pressman  and  prime 
minister,  message-boy  and  millionaire  re- 
spond not  merely  to  their  respective  call- 
bells,  nor  in  common  to  the  peal  of  general 
rejoicing,  to  the  tolling  of  sorrow;  but  through 
their  minds  there  vibrates  also  a  certain  uni- 
son, a  response,  though  it  may  be  more  or  less 
unconscious,  to  the  key-notes  of  their  age. 
How  this  unison  underlies  the  apparent 
differences  is  easily  seen  on  differing  intel- 
lectual levels.  The  boy  in  the  train  buys 
Tit-Bits,  but  the  man  in  the  villa  takes  in  the 
new  Britannica;  the  specialist  concentrates 
upon  the  "Proceedings"  of  his  learned  so- 
ciety, while  the  university  principal  reviews 
his  "Calendar"  of  all  the  studies:  so  far  they 
seem  widely  apart.  But,  after  all,  their  dif- 
ferences are  only  of  degree  and  not  of  kind; 

vu 


viii  INTRODUCTION 

all  four  are  children  of  the  recent  and  passing 
phase  of  knowledge,  characterized  by  the 
encyclopaedia — whether  in  "articles"  or  in 
"papers,"  in  lecture-courses  or  in  snippets 
from  them — all  is  but  a  question  of  magni- 
tude, a  matter  of  detail.  All  four  readers 
alike  are  interested  in  knowledge  of  one  sort 
or  another;  but  these  are  seen  mainly  as 
knowledges,  and  as  advancing  analyses, 
rather  than  as  a  growing  synthesis.  So, 
though  they  all  read  very  different  news- 
papers, these  newspapers  are  yet  much  the 
same,  all  vividly  retrospective  of  yesterday, 
and  keenly  criticizing  such  and  such  of  its 
doings,  but  as  yet  with  little  sight  of  how  the 
day's  items  are  resultants  of  far  distant 
yesterdays,  sowings  for  far  distant  morrows. 
Yet  ideas  of  unity  amid  diversity,  of  order 
amid  change,  have  also  long  been  growing, 
even  finding  expression,  and  this  not  merely, 
as  sporadically  in  all  ages,  in  impressions  and 
speculations  on  decline  or  on  better  things; 
but  in  clearer  and  more  comprehensive  sur- 
veys of  the  processes  of  change,  even  inquiries 
into  its  method.  These,  in  fact,  have  gone 
towards  making  up  that  general  idea  we  now 
more  or  less  share,  of  the  universe  as  not  only 
orderly,  but  in  process  of  change.  Changing 
order,  orderly  change,  and  this  everywhere 
— in  nature  inorganic  and  organic,  in  indi- 


INTRODUCTION  ix 

vidual  and  in  social  life — for  this  vast  con- 
ception, now  everywhere  diffusing,  often 
expressed,  rarely  as  yet  applied,  we  need 
some  general  term — and  this  is  Evolution. 

Now,  if  this  be  gaining  ground  as  a  con- 
ception of  the  world-process,  it  is  time  to  be 
inquiring  farther  into  it:  how  is  this  to  be 
done?  On  one  hand  historically,  thus  cjuickly 
appropriating  the  best  thought  as  yet  reached 
by  others;  on  the  other  hand  directly,  at  first 
hand  and  for  oneself,  in  our  own  environment 
of  life  and  work  and  contact  with  nature.  In 
the  former  way  we  shall  save  time,  and  in  the 
latter  gain  definiteness;  hence  impartially 
deciding  on  both,  we  may  most  speedily  turn 
for  our  outlines  to  our  encyclopaedia,  say 
Chambers'  articles  "Evolution"  and  "Dar- 
winian Theory"  ;  and  for  direct  experience 
take  a  holiday  in  the  woods  or  by  the  shore. 
At  first  the  general  ideas  of  our  reading,  the 
details  of  our  field-observing,  may  seem  to 
haye  little  in  common,  like  the  old  philosopher 
and  the  boy  collector  among  our  acquaint- 
ances: but  gradually  they  come  together: 
orderly  change  in  general,  changing  order 
amid  particulars,  are  more  and  more  seen  to 
be  at  one:  thus  we  become  evolutionists.  We 
hear  of  boy  collectors  becoming  old  philos- 
ophers, yet  remaining  boy  collectors  still: 
Darwin   above  all.      Among    his    foremost 


X  INTRODUCTION 

fellows,  Wallace,  Haeckel,  Hooker  are  still 
with  us;  and  later  ones  in  increasing  number. 
Observing  and  thinking,  thinking  and  observ- 
ing; outdoor  and  indoor,  and  outdoor  again; 
that  is  a  game  at  which  we  all  can  play; 
with  education  and  evolution  alike  mingled 
in  its  process  and  in  its  winning. 

Evolution  in  astronomy,  from  Kant  to 
Lockyer;  evolution  in  chemistry  and  physics, 
from  Lucretius  to  the  alchemists,  and  thence 
to  Ramsay  and  his  fellow-alchemists  of  to- 
day; evolution  in  geology,  from  Leonardo  and 
Palissy  to  L^^ell  and  Darwin  and  onwards  — 
all  these  large  retrospects  of  the  history  of 
science  are  needed  for  a  grasp  of  cosmic 
evolution.  Their  impetus,  their  methods  too, 
have  once  and  again  impelled  the  student  of 
organic  nature  towards  evolutionary  inter- 
pretations, and  still  do  so;  while  the  thought 
of  the  physicist  and  of  the  naturalist  are  in- 
creasingly of  interest  and  suggestion  towards 
the  distinctively  human  and  social  studies. 

Yet  it  was  essentially  in  the  very  opposite 
way  that  modern  evolution  doctrines  really 
originated;  as  a  social  theory,  that  of  progress: 
and  this  generally  diffused  spirit  of  the  later 
eighteenth  century,  and  the  earlier  nine- 
teenth, has  both  consciously  and  uncon- 
sciously stimulated  naturalist  and  physicist 
towards    their    evolutionary    inquiries    and 


INTRODUCTION  xi 

doctrines.  Of  this  social  ferment  of  evolu- 
tionary thought  there  have  been  as  yet  two 
main  phases;  and  first  the  French  eighteenth 
century  "Progress  of  Humanity,"  that  char- 
acteristic doctrine  of  the  Encyclopedists  and 
Physiocrats,  of  Rousseau,  and  of  the  Revo- 
lution at  its  best,  and  this  expressed  for 
history  by  Condorcet,  for  living  nature  by 
Lamarck.  The  second  phase  is  that  of  the 
Industrial  Revolution  in  Britain,  from  Watt 
and  Arkwright  to  Stephenson  and  Wheat- 
stone;  and  thence  to  a  nineteenth-century 
manufacturing  and  commercial  world-pre- 
dominance, proportionately  culminating  from 
1851  to  1860  or  thereby;  with  its  character- 
istic "self-made  men,"  its  colonial  expan- 
sion and  growing  empire. 

It  was  the  former  period,  with  its  theories 
of  society  and  of  morals,  which  gave  birth 
to  the  "Doctrine  of  Evolution";  while  the 
latter  period,  with  its  competitive  industry, 
its  resultant  "population  question,"  etc.,  has 
found  its  expression  in  the  "Doctrine  of 
Natural  Selection."  Each  of  these  two  great 
advances  of  thought  is  thus  the  philosophic 
epic  of  a  great  nation  at  its  epoch;  and 
Lamarck  and  Darwin  are  their  representative 
prophets  respectively. 

In  the  generation  after  Darwin  research 
was  necessarily  actively  specialized  in  biology; 


xii  INTRODUCTION 

and  the  social  perspective,  with  its  conscious 
application  to  evolutionary  research,  has  been 
little  employed  by  naturalists  since  Darwin 
and  Wallace,  despite  its  extraordinary 
fruitfulness  in  their  hands.  Now,  however, 
it  begins  to  return,  witness  the  Eugenic 
movement:  and  in  these  pages  we  shall  not 
hesitate  to  avail  ourselves  of  it. 

We  may  even  utilize  it  for  teaching  pur- 
poses, beginning  with  the  doctrine  of  natural 
selection.  As  Paley's  famous  "watch  argu- 
ment" appeared  at  the  outset  of  the  me- 
chanical age,  so  again  at  its  culmination 
we  may  avail  ourselves  of  the  conspicuous 
progress  of  invention  to  explain  and  illustrate 
Darwin's  great  doctrine.  In  fact,  we  may 
socratically  elicit  it  from  the  freshman  who 
supposes  himself  quite  unacquainted  with 
biology  or  its  theories.  For  he  knows  the 
points  of  a  bicycle,  and  something  of  the 
story  of  its  development  from  his  father's 
"bone-shaker,"  at  one  time  by  the  introduc- 
tion of  ball-bearings,  at  another  by  the  inven- 
tion of  pneumatic  tyres,  each  new  make, 
thanks  to  this  or  that  better  "adaptation," 
being  eminently  successful  in  surviving 
against  its  kindred  but  less  developed  com- 
petitors in  the  struggle  for  existence.  From 
bicycle,  or  similarly  motor  or  aeroplane,  we 
pass  readily  enough  to  bicyclist,  to  racehorse 


INTRODUCTION  xlii 

and  bird:  and  we  see  how  we  may  explain 
the  evolution  of  their  swiftness  in  like  man- 
ner. The  man  in  the  street  is  thus  a  Dar- 
winian without  knowing  it,  and  the  world- 
success  of  Darwin's  theory  is  thus  more 
readily  understood;  the  age  had  found  its 
man,   the  hour  its  voice. 

But  what  of  outdoor  nature.^  "The  field 
in  summer,  the  study  in  winter"  is  a  good 
rule,  yet  not  a  sufficient  one;  the  evolution- 
ist's studies  should  as  far  as  possible  include 
both  elements  of  observation  and  interpre- 
tation day  by  day.  Hence  Darwin's  is  per- 
haps the  most  exemplary  of  scientific  lives, 
incessantly  rising  from  sight  to  insight,  yet 
this  as  constantly  freshening  sight  anew. 
From  boyish  truancies,  through  youthful 
travels  and  maturing  researches  his  observa- 
tions and  his  speculations  went  on  enriching 
one  another;  and  thus  their  interpretation 
and  theory  have  been  an  "  open  sesame"  to 
new  fields,  new  volumes  of  personal  discovery, 
new  impulses  to  fresh  workers.  Naturalist 
and  thinker,  teacher  and  pupil,  will  thus 
long  be  inspired  by  the  example  of  Darwin 
as  rambler,  traveller  and  observer,  yet  also 
as  dreamer  and  interpreter.  The  study  of 
biology  is  thus  by  no  means  merely  abstract, 
nor  mainly  in  the  library;  it  ever  arises  from 
and  returns  to  living  nature,  and  goes  on 


XIV  INTRODUCTION 

througliout  that  annual  season-drama  of 
which  we  are  but  the  awakening  spectators. 

So  psychology  has  its  concrete  nature- 
observation  in  child  study,  in  animal  be- 
haviour; and  just  as  ethics  has  its  side  of 
everyday  life,  so  sociology  its  current  events. 
Nature  studies  and  social  studies  must  again 
be  generalized,  and  this  not  only  separately 
but  in  unison.  How  so?  By  and  from 
Regional  Survey.  Relief  and  climate,  geo- 
logical and  botanical  surveys,  anthropological, 
archseological  and  historic  surveys  all  under- 
lie our  social  studies.  Our  concrete  science 
thus  generalizes  into  a  comprehensive  re- 
gional survey,  natural  and  social,  rural  and 
urban;  as  our  abstract  sciences  advance  and 
unite  into  a  philosophy  of  evolution.  In 
measure  as  our  abstract  interpretations  and 
our  concrete  surveys  come  together  and 
unify,  our  geography  becomes  geogeny,  that 
is,  it  develops  from  mere  empirical  world- 
description  into  a  rational  vision  of  world- 
development.  And  correspondingly,  the 
abstract  of  this,  which  is  our  evolution 
doctrine,  becomes  applicable  in  education 
and  in  social  life. 

Enough,  then,  of  introductory  outline;  in 
the  following  chapters  we  endeavour  to  eluci- 
date some  of  these  large  propositions  more 
clearly. 


EVOLUTION 


CHAPTER   I 

EVIDENCES    OF    EVOLUTION    FROM     EXPLORER 
AND    PALEONTOLOGIST 

The  Voyage  of  the  "Beagle"  —  The  Galapagos  Islands  — 
Other  Geographical  Evidence  —  Resemblances  of  Present 
Forms  and  Past  Ones  —  The  Ancestry  of  the  Horse  — • 
Connecting  Links  —  Other  Palseontological  Evidences. 

The  Voyage  of  the  "Beagle." — We  think 
of  the  voyage  of  the  "  Challenger  "  as  a  Co- 
lumbus-voyage in  the  history  of  Biology, 
for  it  revealed  a  new  world  —  the  strange, 
silent,  cold,  dark,  plantless  world  of  the 
abyssal  sea.  But  a  far  greater  Columbus- 
voyage  was  that  of  the  "Beagle"  (18S1-6), 
which  led  Darwin,  as  the  supreme  field- 
naturalist,  at  once  widest  and  intensest,  to 
make  the  whole  world  new.  For  it  was  during 
this  voyage  that  the  evolutionist  view  of 
Nature  was  vitally  borne  in  on  Darwin's 
mind.  He  tells  us  so  himself:  "On  my  return 
home  in  the  autumn  of  1836  I  immediately 
began  to  prepare  my  journal  for  publication, 
and  then  saw  how  many  facts  indicated  the 

PKOKMTY  UBRAKY 

ILCSUUe  CMege 


16  EVOLUTION 

common  descent  of  species.  ...  In  July 
(1837)  I  opened  my  first  notebook  for  facts  in 
relation  to  the  Origin  of  Species,  about  which 
I  had  long  reflected,  and  never  ceased  work- 
ing for  the  next  twenty  years.  .  .  .  Had  been 
greatly  struck  from  about  the  month  of  pre- 
vious March  on  character  of  South  American 
fossils,  and  species  on  Galapagos  Archipelago. 
These  facts  (especially  latter)  origin  of  all  my 
views." 

This  interesting  biographic  fact,  that  what 
Darwin  saw  on  the  Galapagos  Islands  and 
elsewhere  on  his  journeyings  was  (or  at  least 
seemed  to  him)  the  origin  of  all  his  views, 
justifies  us  in  giving  precedence  to  the  "evi- 
dences" of  evolution  that  have  come  from 
his  and  other  explorations. 

The  Galapagos  Islands.  —  Let  us  take 
the  case  of  these  islands  (some  six  hundred 
miles  west  of  the  coast  of  South  America), 
which  impressed  Darwin  so  much  when  he 
visited  them  in  1835.  What  exactly  was  it 
that  impressed  him?  He  found  that  each 
island  had  its  own  distinctive  animal  popu- 
lation, especially  of  reptiles  and  birds.  And 
yet  the  species  in  one  island  were  the  counter- 
parts of  those  in  another,  and  almost  all  had 
their  counterparts  in  the  adjoining  parts  of 
the  continent.  What  a  riddle  indeed  —  unless 
it  meant  that  the  corresponding  species  on 


EVIDENCES   OF  EVOLUTION        17 

the  different  islands  and  on  the  continent 
were  blood-relations  with  a  common  de- 
scent? Thus  it  was  that  in  the  Galapagos 
Archipelago  Darwin  felt  himself  "brought 
near  to  the  very  act  of  creation." 

"My  attention,"  Darwin  writes,  "was  first 
thoroughly  aroused  by  comparing  together 
the  numerous  specimens,  shot  by  myself  and 
several  other  parties  on  board,  of  mocking 
thrushes,  when,  to  my  astonishment,  I  dis- 
covered that  all  those  from  Charles  Island 
belonged  to  one  species  (Mimus  trif asciatus) ; 
all  from  Albemarle  Island  to  M.  parvulus; 
and  all  from  James  and  Chatham  Islands 
(between  which  two  other  islands  are  situ- 
ated as  connecting  links)  belonged  to  M. 
melanotis." 

All  subsequent  investigations  have  con- 
firmed Darwin's  observations,  both  in  their 
general  result  and  in  details.  Thus  it  has 
since  been  shown  by  Ridgway  that  the 
thrushes  from  James  and  Chatham  Islands 
of  the  same  group  are  also  of  distinct  species. 
And  of  one  hundred  and  twenty-eight  speci- 
mens of  a  lizard  called  Tropidurus  collected 
by  the  "Albatross"  from  eight  of  the  islands, 
Dr.  Baur  writes  just  as  Darwin  did:  "I  was 
not  a  little  astonished  to  find  that  nearly 
every  island  contained  a  peculiar  race  of 
species  of  this  lizard,  and  that  not  a  single 


18  EVOLUTION 

island  contained  more  than  one  race  or 
species."  The  same  is  true  of  the  tortoises 
and  the  birds,  and  no  scientific  interpretation 
has  been  suggested  except  that  which  Dar- 
win gave  —  of  divergent  evolution  from  a 
common  stock. 

We  cannot  here  enter  into  a  discussion  of 
the  geological  history  of  the  Galapagos  Isl- 
ands, in  regard  to  which  there  is  some  differ- 
ence of  opinion;  it  must  suffice  to  state  one 
of  the  theories — that  advanced  by  Baur  in 
the  Woods  HoU  Biological  Lectures  for  1894. 
"At  a  former  period  these  islands  were  con- 
nected with  each  other,  forming  a  single 
large  island,  which  itself  at  a  still  earlier 
time  was  united  with  the  continent,  probably 
with  Central  America  and  the  West  Indies. 
When  this  large  island  was  not  yet  broken  up 
into  a  series  of  smaller  islands,  the  number  of 
species  must  have  been  very  much  smaller; 
probably  there  was  only  one  species  of  Neso- 
mimus,  of  Certhidia,  of  Tropidurus,  of  the 
Land  Tortoise,  and  so  on.  Through  isola- 
tion into  single  islands  the  peculiar  differen- 
tiation of  the  species  began;  an  originally 
single  species  was  differentiated  in  many 
different  forms;  every,  or  nearly  every, 
island  developed  its  peculiar  races.  We  still 
see  to-day  that  islands  which  are  close  to- 
gether and  not  separated  by  deep  water  show 


EVIDENCES  OF  EVOLUTION         19 

the  same  species,  like  James  and  Jervis,  or 
Hood  and  Gardner.  The  faunas  of  the 
larger  central  islands  are  again  more  closely 
related  to  each  other  than  are  the  faunas  of 
the  more  isolated  islands  like  Tower,  Bindloe, 
Abingdon,  Hood  and  Charles.  The  tortoise 
of  Duncan  is  closest  to  the  tortoise  from  Ab- 
ingdon; at  the  same  time  the  Tropidurus  of 
Duncan  comes  nearest  to  that  of  Abingdon. 
The  prevention  of  intercrossing  after  the 
separation  of  the  islands,  the  time  of  separa- 
tion, and  the  difference  in  the  conditions  on 
the  different  islands,  are  the  factors  which 
produce  the  different  races." 

We  may  also  refer  the  student  to  Wallace's 
fascinating  "Island  Life"  for  further  illus- 
trations of  the  evolutionary  suggestiveness  of 
the  exploration  of  islands. 

Other  Geographical  Evidences. — As  in 
other  parts  of  this  little  book  we  have  dwelt 
on  one  interesting  illustration  of  a  large 
subject,  we  cannot  do  more  than  refer  briefly 
to  some  of  the  other  geographical  evidences. 

With  the  help  of  the  palaeontologist  it  is 
sometimes  possible  to  come  to  a  conclusion  as 
to  the  original  headquarters  of  a  particular 
race  of  plants  or  animals,  and  then  it  is  found 
that  the  present-day  distribution  of  the 
members  of  the  race  is  readily  intelligible  on 
the  evolutionary  assumption  of  diffusion  from 


20  EVOLUTION 

the  original  centre,  and  of  transformation 
into  new  species  in  relation  to  the  new  con- 
ditions encountered.  Some  of  the  particular 
case  leap  to  the  eye,  but  they  are  unmeaning 
conundrums  without  the  evolutionist  clue. 
Darwin  has,  in  fact,  brought  us  more  nearly 
back  to  the  Noah's  ark  of  our  childhood  than 
we  commonly  realize;  for  do  not  all  these 
stories  of  thrushes,  lizards  and  what  not 
quaintly  recall  the  origin  of  human  races  from 
the  dispersion  of  Shem,  Ham  and  Japheth.f^ 

In  Mesozoic  times,  when  there  were  no 
Mammals  higher  than  Marsupials,  Australia 
was  separated  off  from  the  Asiatic  continent. 
Therefore  it  is  that  there  are  no  higher 
Mammals  in  Australia,  except  the  somewhat 
mysterious  dingo,  the  bats,  which  find  the  sea 
no  barrier,  and  the  rabbits,  for  which  man 
is  responsible. 

A  final  argument  is  furnished  by  the  con- 
trast in  the  fauna  and  flora  of  oceanic  and  of 
continental  islands.  The  former,  being  usu- 
ally of  volcanic  origin,  have  always  a  very 
distinctive  fauna  and  flora,  which  Wallace 
has  explained  as  being  due  to  the  fortuitous 
contributions  borne  from  diverse  quarters  by 
currents,  winds  and  birds.  Other  islands, 
which  are  isolated  pieces  of  continents,  have 
a  fauna  and  flora  like  that  of  the  nearest  part 
of  the  mainland. 


EVIDENCES  OF  EVOLUTION        21 

Hesemblances  of  Present  Forms  and 
Past  Ones.  —  Another  seed-impression  that 
was  borne  in  on  Darwin's  mind  during  his 
journeyings  was  the  striking  resemblance 
between  the  living  and  the  extinct  forms  in 
the  same  area.  On  his  travels  into  the  inte- 
rior of  South  America  he  made  large  collec- 
tions, both  of  living  animals  and  of  fossils 
dug  from  the  red  mud  of  the  Pampas,  and 
what  impressed  him  most  was  that  the  ex- 
tinct bore  a  notable  correspondence  to  the 
extant.  No  living  creatures  are  more  char- 
acteristic of  the  South  American  fauna  than 
the  sloths  and  ant-eaters;  no  fossils  are  more 
characteristic  than  the  gigantic  Megathe- 
riums and  Glyptodonts;  and  the  important 
fact  is  the  structural  resemblance  between 
these  creatures  of  the  past  and  those  of  the 
present — a  structural  resemblance  which 
suggested  to  Darwin  that  the  explanation 
might  be,  indeed  must  be,  one  of  blood- 
relationship.  "  This  wonderful  relation- 
ship," he  wrote,  "in  the  same  continent 
between  the  dead  and  the  living  will,  I 
do  not  doubt,  hereafter  throw  more  light  on 
the  appearance  of  organic  beings  on  our 
earth,  and  their  disappearance  from  it,  than 
any  other  class  of  facts."  This  is,  to  be  sure, 
a  cautious  statement;  but  it  seems  not  un- 
likely that  it  was  while  thus  digging  his 


22  EVOLUTION 

fossils  on  the  Pampas  that  Darwin  laid  vital 
hold  upon  the  principle  long  nascent  in  geol- 
ogy, and  especially  impressed  apon  him  by 
Lyell,  that  the  present  is  the  child  of  the 
past — an  idea  which  he  spent  so  much  of  his 
life  in  substantiating.  Let  us  consider  some 
other  illustrations  of  the  palseontological 
evidence. 

Fossil  Horses. — Huxley  made  a  strong 
statement  in  1855  as  to  the  futility  of  seeking 
in  the  study  of  fossils  for  confirmation  of  the 
doctrine  of  evolution,  but  after  a  quarter  of  a 
century  of  investigation  he  was  as  strongly  of 
the  opposite  opinion,  declaring  that  "if  zoolo- 
gists and  embryologists  had  not  put  forward 
the  theory,  it  would  have  been  necessary  for 
palseontologists  to  invent  it."  One  of  the 
many  reasons  which  led  him  to  a  warm  appre- 
ciation of  "the  palseontological  evidence," 
was  a  visit  to  America,  where  he  saw  the 
famous  series  of  fossil  horses  which  Marsh  had 
unearthed  from  American  Tertiary  beds — 
one  of  the  most  impressive  of  pedigrees  that 
has  yet  been  disclosed.  For  although  we  are 
not  even  now  able  to  state  the  lineage  of  the 
modern  horse,  the  chief  steps  in  the  evolu- 
tionary process  stand  out  with  clearness,  and 
he  must  be  dull  indeed  who  can  see  the  ad- 
mirably arranged  and  convincing  series  in 
the  museums  at  Yale  and  New  York  without 


EVIDENCES  OF  EVOLUTION        23 

a  thrill  of  admiration  at  the  wonderful  recon- 
struction of  the  ancient  history  of  the  noblest 
race  of  animals,  and  that  most  widely  identi- 
fied with  man.  Since  Huxley's  day  the 
fossil  horse  has  been  "the  cheval  de  hataille  of 
the  evolutionist." 

In  spite  of  many  puzzles,  the  pedigree  is 
one  of  the  completest  and  most  striking  in- 
stances of  a  well-preserved  genealogical 
series.  It  illustrates  evolution,  as  it  were,  in 
process,  for  the  gradations  are  very  gradual; 
and  natural  selection  also,  for  the  advances 
in  the  adaptation  of  the  limbs  to  swifter  lo- 
comotion, of  the  neck  to  reach  the  low  grass, 
of  the  teeth  for  more  effective  chewing,  and 
so  on,  are  all  such  as  may  be  reasonably  in- 
terpreted in  terms  of  the  selection  of  rela- 
tively better-fitted  variations.  Let  us,  since 
the  case  is  a  classic  one,  attempt  an  outline 
of  the  geological  history  of  the  horse  family, 
following  the  careful  work  of  the  successors 
of  Marsh  and  Cope,  notably  of  Lull  and 
Matthew. 

The  horse-like  animals  probably  sprang 
from  an  extinct  stock  known  as  the  Condyle 
arthra,  which  was  first  represented  in  Europe 
and  Asia,  and  afterwards  in  North  America. 
The  Condylarthra  had  five  toes  on  each  foot 
and  a  large  part  of  the  sole  was  on  the  ground. 
One  of  them,  Phenacodus,  was  called  by  its 


24  EVOLUTION 

discoverer,  Professor  E..D.  Cope,  a  "five-toed 
horse,"  but  this  is  not  to  be  taken  too  hterally. 
"The  first  undoubted  horse-like  animal 
appearing  in  the  rocks  of  North  America  is  a 
little  creature  not  more  than  eleven  inches 
high,  known  to  science  as  Eohippus.  This 
interesting  animal  had  already  made  a  long 
stride  in  the  direction  of  the  modern  horse,  as 
the  number  of  toes  is  now  reduced  to  four  in 
front  and  three  behind,  and  the  bones  of  the 
wrist  and  ankle  have  shifted  so  as  to  inter- 
lock, which  greatly  strengthens  the  foot." 
It  seems  that  Eohippus  was  also  represented 
in  Britain,  and  it  is  possible  that  migrants 
by  way  of  Asia  and  what  is  now  the  Behring 
Strait  started  the  American  stock.  Appar- 
ently more  primitive  than  Eohippus  is  the 
"coney-like  creature"  Hyracotherium,  but 
only  the  skull  is  known.  "Commencing 
with  the  Hyracotherium,"  Dr.  Matthew 
writes,  "twelve  stages  have  been  recognized 
from  as  many  successive  formations,  showing 
the  gradual  evolution  of  the  race  into  its 
modern  form;  and  each  stage  is  characteris- 
tic of  its  particular  geological  horizon.  Be- 
sides the  main  line  of  descent  which  led  into 
the  modern  horses  and  zebras,  there  were 
several  collateral  branches  which  have  left 
no  descendants." 

Also  in  the  Eocene  there  was  Protorohip- 

iL  C.  Smu  CoUtM 


EVIDENCES  OF  EVOLUTION        25 

pus,  with  four  toes  in.  front  and  three  behind, 
the  side  ones  behind  touching  the  ground.  It 
seems  to  have  been  about  fourteen  inches 
high,  and  the  evolution  of  speed  had  begun. 
During  the  Eocene  times  North  America  was 
in  great  part  forest-clad,  but  "the  moist 
climate  gave  rise  to  many  streams  and  lakes, 
along  the  shores  of  which  grew  sedgy  mead- 
ows that  in  turn  gave  rise  to  grassy  plains. 
These  were  the  conditions  under  which  the 
horses  made  their  first  appearance,  and  the 
increasing  development  of  grass  lands  gave 
the  initial  trend  to  their  evolution." 

Somewhat  later,  in  the  Oligocene,  Meso- 
hippus  makes  its  appearance,  the  hind-foot 
with  three  toes  as  before,  but  the  fore-foot 
with  the  little  toe  reduced  to  a  splint,  so  that 
only  three  remain,  the  side  ones  just  touch- 
ing the  ground.  The  middle  or  third  toe  is 
now  much  larger  than  the  side  toes,  which  no 
longer  bear  much  of  the  weight  of  the  animal, 
save  on  marshy  ground.  The  grinding  teeth 
have  become  more  complex.  One  of  the 
species  of  Mesohippus  was  about  the  size  of 
a  sheep,  and  one  of  the  treasures  in  the  Yale 
Museum  that  brings  the  past  very  vividly 
back  to  us  is  the  nearly  perfect  skull  of  its 
new-born  foal.  Of  the  physical  conditions 
of  the  Oligocene,  Dr.  Lull  writes:  "The  dry- 
ing  up  of  streams  and  lakes,  due  to  the 


26  EVOLUTION 

increasing  aridity  of  climate,  gave  great  im- 
petus to  the  development  of  broad  meadow 
lands,  and  to  the  true  prairie  as  well.  Thus 
there  were  three  conditions — woodland,  mead- 
ows and  dry  prairie,  which  seem  to  have 
given  rise  to  several  parallel  lines  of  evolution, 
some  of  which  terminated,  being  overcome 
in  the  struggle  for  existence,  while  others 
flourished  and  gave  rise  to  the  horses  of  the 
Miocene." 

Of  the  Miocene  types  we  may  select  Pro- 
tohippus,  with  three  toes  on  each  foot,  but 
only  one  touching  the  ground.  The  short- 
crowned  teeth  without  cement  are  now  re- 
placed by  long-crowned  cement-covered  teeth 
like  those  of  the  modern  horse.  Protohippus 
was  about  thirty-six  inches  high  at  the  shoul- 
der, and  had  a  wide  distribution  from  Texas 
to  Montana  and  Oregon.  In  a  closely  re- 
lated genus,  Merychippus,  we  find  the  first 
instance  of  the  completion  of  a  bridge  of  bone 
at  the  hinder  border  of  the  orbit,  one  of  the 
characteristic  differences  between  the  skull 
of  a  horse  and  that  of  a  carnivore,  for  in- 
stance. Merychippus  is  of  particular  inter- 
est, because  it  is  almost  certainly  in  the 
direct  line  of  ancestry  to  all  subsequent 
Equidse.  The  forest-horse,  Hypohippus, 
with  spreading  three-toed  feet,  suited,  like 
the  reindeer's,  for  soft  ground,  is  a  good  ex- 


EVIDENCES  OF  EVOLUTION        27 

ample  of  those  horses  that  became  extinct 
during  the  Miocene,  leaving  no  descendants, 
and  Anchitherium,  found  both  in  Europe  and 
in  America,  was  probably  also  on  a  side 
branch.  Of  the  Miocene  period.  Dr.  Lull 
says:  "This  was  a  time  of  continental  eleva- 
tion and  great  expansion  of  our  western 
prairies  and  a  consequent  diminution  of  the 
forest-clad  areas."  Many  forms  very  per- 
fectly adapted  to  soft  herbage  became  ex- 
tinct, "but  the  great  majority  were  more 
plastic  and  in  consequence  underwent  a 
remarkable  development,  during  this  period 
reaching  the  culmination  in  numbers  and 
kinds." 

In  the  Pliocene  there  was  a  wide  repre- 
sentation of  the  Old  World  genus  Hipparion, 
most  of  the  species  still  three-toed.  It  was 
probably  derived  from  the  American  Neo- 
hipparion,  a  swift,  deer-like  animal,  about 
forty  inches  in  height  at  the  shoulder.  "In 
the  Siwalik  beds  of  India  is  found  a  one-toed 
Hipparion,  and  it  has  been  suggested  that 
the  modern  zebras  may  be  the  living  descend- 
ants of  this  genus.  It  is  certainly  not  in  the 
line  to  the  common  horse,  Equus  caballus, 
which  makes  its  appearance,  however,  in  the 
Upper  Pliocene  beds  both  of  Eurasia  and 
North  America — the  climax  of  a  long  evo- 
lutionary progression." 


28  EVOLUTION 

We  have  dwelt  on  the  case  of  the  horse's 
pedigree — at  once  longer  and  stranger  than 
any  fairy  ride — because  it  is  one  of  the  best 
instances  of  its  kind,  and  from  one  such  we 
may  learn  all.  But  we  have  only  given  the 
bare  outlines  of  a  remarkable  story,  well 
worth  reading  in  detail.  In  the  enthusiasm 
of  early  discoveries  the  matter  seemed  simpler 
than  it  really  is,  and  the  mistake  was  made 
of  hurriedly  constructing  a  linear  series  which 
showed,  for  instance,  the  gradual  reduction 
of  toes  from  five  to  one,  and  supposing  that 
this  was  a  genuine  pedigree.  More  detailed 
and  critical  inquiry  has  shown,  however,  that 
there  were  several  collateral  series,  and  it  is 
not  quite  justifiable  to  fill  up  gaps  along  one 
line  by  links  which  belong  to  other  lines  of 
descent.  One  critic  points  out  that  Equus 
actually  appears  in  the  rock  record  before 
some  of  its  alleged  ancestors,  and  Deperet 
writes  in  his  interesting  "Transformations 
of  the  Animal  World":  "The  supposed  pedi- 
gree of  the  Equidse  is  a  deceitful  delusion, 
which  simply  gives  us  the  general  process  by 
which  the  tridactyl  hoof  of  an  Ungulate  can 
transform  itself,  in  various  groups,  into  a 
monodactyl  hoof,  in  view  of  an  adapta- 
tion for  speed."  It  is  interesting  to  notice, 
however,  that  among  competent  critics  of 
too  hastily  constructed  pedigrees  even  the 


EVIDENCES  OF  EVOLUTION        29 

severest  do  not  in  the  least  impugn  the  doc- 
trine of  evolution. 

What  seems  clear  is  this,  that  in  early 
Eocene  times  there  lived  small  five-toed 
hoofed  quadrupeds  of  generalized  type,  that 
the  descendants  of  these  were  gradually 
specialized  throughout  long  ages  along  similar 
but  by  and  by  divergent  lines,  that  they  lost 
toe  after  toe  till  only  the  third  remained, 
that  they  became  taller  and  swifter,  that  they 
gained  longer  necks,  more  complex  teeth  and 
larger  brains.  So  from  the  short-legged  splay- 
footed plodders  of  the  Eocene  marshes  there 
were  evolved  light-footed  horses  running  on 
tiptoe  on  the  dry  plains. 

We  can  only  refer  to  the  importance  for  an 
evolutionist  outlook  of  thus  trying  to  corre- 
late the  changes  in  the  animal  with  the 
changes  in  the  external  conditions.  The  evo- 
lution of  the  horse  is  wrapped  up  with  the 
evolution  of  the  plains,  and  of  their  grasses 
also,  for  these  made  their  first  appearance 
in  Tertiary  times.  The  early  ancestors  prob- 
ablv  lived  in  the  warm  luxuriant  forests, 
but  as  colder,  drier  climate  set  in,  and  the 
forests  shrank,  the  progressive  "hippoids" 
took  more  and  more  to  the  open.  Even  in 
regard  to  the  teeth  we  can  understand  that 
the  change  from  the  short-crowned  to  the 
long-crowned  type  enabled  the  animals,  as 


30  EVOLUTION 

Dr.  Matthew  notices,  "to  subsist  on  the 
hard,  comparatively  innutritions  grasses  of 
the  dry  plains,  which  require  much  more 
thorough  mastication  before  they  can  be  of 
any  use  as  food  than  do  the  softer  green  foods 
of  the  swamps  and  forests." 

We  must  not  leave  this  question  of  the 
horse's  evolution  without  calling  attention  to 
a  fact  of  great  interest,  that  in  the  individual 
development  there  is  a  series  of  changes 
which  to  some  extent  correspond  with  the 
historical  steps  represented  by  forms  like 
Eohippus,  Mesohippus,  Protohippus,  Mery- 
chippus,  and  so  on.  Professor  Cossar  Ewart 
has  shown,  for  instance,  that  the  small  nodule 
at  the  end  of  the  splint  bone  is  separate  in 
the  embryo,  and  is  the  representative  of 
one  or  more  of  the  joints  of  the  second  or  the 
fourth  digit  which,  apart  from  this,  would 
seem  to  have  entirely  passed  away.  It  is 
well  known  that  in  a  monstrosity  of  our 
familiar  one-toed  horse  the  splint  bone  on 
each  side  of  the  main  cannon-bone  is  en- 
larged, and  bears  a  complete  digit,  so  that  a 
three-toed  horse,  such  as  the  one  Julius 
Csesar  rode,  occasionally  still  walks  upon  the 
earth.  Such  cases  of  symmetrical  three-toed 
development  may  be  fairly  interpreted  as 
reversions  to  the  ancestral  type,  and  are  to 
be   distinguished  from  unsymmetrical  extra 


EVIDENCES  OF  EVOLUTION        31 

toes,  which  are  mere  duplications  without 
ancestral  interest,  and  comparable  to  the 
occasional  occurrence  of  a  sixth  finger  in  man. 

In  his  very  interesting  study  of  "Wild 
Traits  in  Tame  Animals"  (1897)  Dr.  Louis 
Robinson  refers  to  survivals  of  behaviour 
which  date  from  the  old  wild  life  in  the  open 
plains.  It  was  imperative  long  ago  that  the 
young  foals  should  run  with  their  mothers, 
and  to  this  day  they  do  not  gorge  themselves 
with  milk  as  calves  do.  When  alarmed, 
horses  hold  their  heads  high,  as  when  wild 
upon  the  plains;  they  bite  very  closely  when 
grazing;  in  both  respects  they  differ  markedly 
from  cattle.  "Shying"  is  a  relic  of  the  in- 
stinct of  swerving  suddenly  from  a  suspicious 
rustling  and  the  like  which  used  to  mean  the 
presence  of  a  lurking  foe.  Such  survivals 
are  interesting  and  strike  our  fancy;  but  the 
past  lives  in  the  present  even  more  clearly 
in  regard  to  structure  than  in  regard  to  habit, 
and  by  the  "button"  at  the  lower  end  of  the 
splint  bones  the  modern  horse  is  indubitably 
linked  back  to  its  polydactyl  ancestors. 

Connecting  Links. — There  is  no  more 
complete  or  striking  contrast  of  aspect  and 
habitat,  habit  and  temperament  in  the 
animal  kingdom  than  that  between  the 
average  bird  and  the  average  reptile;  and  yet 
every   zoologist   is   sure   that   birds   sprang 


32  EVOLUTION 

from  some  ancient  reptilian  or  saurian  stock. 
He  has  not  ceased  to  wonder  how  this  tran- 
sition can  have  come  about;  "how  the  slow, 
cold-blooded,  scaly  beast  ever  became  trans- 
formed into  the  quick,  hot-blooded,  feathered 
bird,  the  joy  of  creation";  but  he  does  not 
doubt  that  the  transition  was  effected.  He 
is  still  unwilling  to  make  any  positive  state- 
ment in  regard  to  the  precise  pedigree  of 
birds,  and  yet  he  is  confident  that  they 
sprang  from  a  reptilian  stock.  What  are 
the  reasons  for  this  confidence? 

They  are  threefold: — (1)  There  are,  in  spite 
of  appearances,  numerous  structural  resem- 
blances between  birds  and  reptiles,  from  the 
scales  on  the  feet  to  the  composition  and  the 
articulation  of  the  lower  jaw;  (2)  there  are 
deep  similarities  in  development,  for  the 
embryo  bird  and  the  embryo  reptile  travel 
at  first  along  parallel  paths,  and  only  grad- 
ually part  company;  and  (3)  there  are 
extinct  types  which  to  some  extent  bridge 
the  conspicuous  gap.  A  word,  then,  in  regard 
to  these  connecting  links. 

One  of  the  most  treasured  fossils  in  the 
world — of  which  the  British  Museum  and 
the  Berlin  Museum  have  each  one  of  the 
two  known  specimens — is  the  oldest  known 
bird,  Archseopteryx.  These  priceless  skele- 
tons were  found  well  preserved  in  the  lith- 


EVIDENCES  OF  EVOLUTION        33 

ograpliic  stone  of  Bavaria,  and  the  grain  of 
the  stone — a  hardened  mud — is  so  fine  that 
the  impressions  of  the  feathers  are  well  seen, 
and  most  of  the  bones  are  clear.  Archseop- 
teryx  was  a  creature  about  the  size  of  a  crow, 
probably  arboreal,  and  beyond  all  doubt 
a  bird — the  earliest  bird  we  know  of.  But 
what  gives  it  a  peculiar  interest  is  that  while 
it  is  not  far  from  a  typical  bird  in  its  skull,  its 
merry-thought,  and  its  legs,  it  is  in  some 
other  respects  markedly  reptile-like.  It  has, 
for  instance,  teeth  in  both  jaws,  a  long  tail 
like  a  lizard's,  and  a  strange  wing,  well- 
developed  yet  unfinished,  with  its  three 
digits  ending  in  unmistakable  claws. 

Now  Archseopteryx  was  very  far  from  be- 
ing a  beginner  on  the  bird  line  of  evolution; 
its  wings  and  its  legs  prove  that.  It  is  also 
possible  that  it  was  an  offshoot  from  the 
direct  line,  and  thus  not  ancestral  to  any 
bird  now  living.  Still,  we  cannot  but  regard 
it  as  "a  connecting  link"  in  the  sense  that 
it  shows  in  its  structure  a  combination  of 
reptilian  and  avian  characters,  the  latter,  of 
course,  fully  predominating. 

Fossil  Series. — One  of  the  finest  examples 
of  a  well-preserved  series  of  kindred  forms 
is  afforded  by  an  extinct  freshwater  snail, 
Paludina  neumayri,  which  is  very  abundant 
in  some  Tertiary  deposits  in  Slavonia.    The 


34  EVOLUTION 

oldest  form  has  a  more  or  less  smooth  shell, 
the  youngest  has  a  conspicuously  ridged  shell, 
and  there  are  fifteen  gradations  between  the 
two.  Before  the  complete  series  was  known 
it  was  usual  to  distinguish  half  a  dozen  or 
more  species;  but  with  the  beautifully  gradu- 
ated, really  continuous  series  before  us,  we 
feel — fossils  as  they  are — that  we  see  a  species 
varying  before  our  eyes.  If  conditions  had 
arisen  that  assured  survival  and  success  only 
to  the  markedly  ridged  forms,  the  inter- 
mediate gradations  would  soon  have  fallen 
into  the  minority  and  disappeared  as  living 
creatures  from  the  scene,  and  a  ridged  species, 
apparently  discontinuous,  would  have  been 
established. 

Similarly  in  the  neighbourhood  of  Stein- 
heim  in  Wlirtemberg,  in  calcareous  deposits 
that  mark  the  floor  of  an  old  Tertiary  lake, 
there  are  enormous  quantities  of  a  small 
snail,  Planorbis  multiformis,  which  has 
been  carefully  studied  by  Hyatt  and  others. 
And  again,  since  the  whole  history  has  been 
unearthed,  we  see  evolution  before  our  eyes. 
The  particularly  interesting  feature  is  that 
there  are  four  or  so  primitive  forms  which 
are  very  like  one  another,  and  that  each  of 
these  is  the  starting-point  of  a  series  the 
termini  of  which  are  very  different.  The 
contrast  between  the  beginning  and  the  end 


EVIDENCES  OF  EVOLUTION        35 

of  a  series,  e,  g,  between  a  high  spiral  and  a 
flat  spiral,  is  often  so  striking  that  no  one 
would  hesitate  in  calling  them  distinct 
species.  Yet  they  are  connected  by  a  long 
series  of  fine  gradations. 

Some  are  surprised  that  such  series  are  not 
commoner  if  Evolution  has  been  the  mode  of 
the  becoming  of  things;  but  they  have  not 
adequately  understood  how  great  are  the 
odds  against  the  preservation  of  such  records. 
Only  hard  parts  make  good  fossils;  only  cer- 
tain kinds  of  deposits  make  suitable  tombs; 
many  rocks  have  been  unmade  and  re-made 
several  times; — these  and  many  other  facts 
enable  us  to  understand  "the  imperfection 
of  the  geological  record."  As  Darwin  said, 
we  must  look  at  the  geological  record  "  as  a 
history  of  the  world  imperfectly  kept,  and 
written  in  a  changing  dialect;  of  this  history 
we  possess  the  last  volume  alone,  relating 
only  to  two  or  three  countries.  Of  this 
volume,  only  here  and  there  a  short  chapter 
has  been  preserved;  and  of  each  page,  only 
here  and  there  a  few  lines."  And  again  he 
said:  "We  shall  perhaps  best  perceive  the 
improbability  of  our  being  enabled  to  connect 
species  by  numerous  fine  intermediate  fossil 
links,  by  asking  ourselves  whether,  for  in- 
stance, geologists  at  some  future  period  will 
be  able  to  prove  that  our  different  breeds  of 


36         '  EVOLUTION 

cattle,  sheep,  horses  and  dogs  are  descended 
from  a  single  stock  or  from  several  aboriginal 
stocks.  .  .  .  This  could  be  effected  by  the 
future  geologist  only  by  his  discovering  in 
a  fossil  state  numerous  intermediate  grada- 
tions; and  such  success  is  improbable  in  the 
highest  degree." 

Other  Pal^ontological  Evidences. — 
There  is  a  sublime  suggestiveness  in  the  broad 
fact  that  in  successive  periods  of  the  earth's 
history  higher  and  higher  animals  appear. 
Fishes  make  their  appearance  in  the  Silurian, 
Amphibians  in  the  Carboniferous,  Rep  dies 
in  the  Permian,  and  Birds  in  the  Jurassic. 
The  record  as  regards  plants  is  perhaps  more 
stril^ing  in  some  of  its  details  than  in  its 
broad  outlines  (see  Dr.  Scott's  volume  in  this 
series  on  "The  Evolution  of  Plants"),  but 
every  one  will  allow  that  there  were  Crypto- 
gams before  there  were  Phanerogams,  and 
Cycads  and  Conifers  before  there  were  any 
ordinary  Flowering  Plants. 

There  are  other  sets  of  suggestive  facts  to 
which  reference  might  be  made  if  space  per- 
mitted :  there  is  the  absence  of  sudden  breaks 
or  cataclysms;  there  is  gradual  waxing  and 
waning  of  races;  there  is  the  remarkable 
phenomenon  of  what  may  be  called  the 
adolescence  and  senescence  of  genera,  if  not 
even  species;  there  is  the  occurrence  of  old- 


EVIDENCES  OF  EVOLUTION        37 

fashioned  generalized  types  which  link  to- 
gether a  number  of  now  divergent  stocks;  but 
perhaps  we  have  said  enough  to  show  that 
the  facts  brought  to  light  by  the  explorations 
of  palaeontologists  are  suggestive  of  the 
evolutionist  interpretation,  and  there  is  no 
other  reading  of  the  rock-record  that  does 
not  leave  the  facts  enigmatical.  In  empha- 
sizing the  importance  of  this  line  of  argu- 
ment, Huxley  said:  "The  primary  and  direct 
evidence  in  favour  of  Evolution  can  be  fur- 
nished only  by  palaeontology.  The  geological 
record,  so  soon  as  it  approaches  completeness, 
must,  when  properly  questioned,  yield  either 
an  affirmative  or  a  negative  answer:  if  Evo- 
lution has  taken  place  there  will  its  mark  be 
left;  if  it  has  not  taken  place  there  will  lie  its 
refutation."  But  it  is  more  consistent  with 
the  science  of  to-day  to  put  the  case  more 
confidently,  and  we  would  quote  the  opinion 
of  a  living  palaeontologist  of  high  achieve- 
ment, Professor  W.  B.  Scott  of  Princeton: 
"The  geological  record  is  not  so  hopelessly 
incomplete  as  Darwin  believed  it  to  be.  Since 
*The  Origin  of  Species'  was  written  our 
knowledge  of  that  record  has  been  enor- 
mously extended,  and  we  now  possess  no 
complete  volumes,  it  is  true,  but  some  re- 
markably full  and  illuminating  chapters. 
The  main  significance  of  the  whole  lies  in  the 


38  EVOLUTION 

fact  that,  just  in  proportion  to  the  complete- 
ness of  the  record  is  the  unequivocal  character 
of  its  testimony  to  the  truth  of  the  evolutionary 
theory. " 

The  wealth  and  interest  of  the  palaeonto- 
logical  record  is,  in  fact,  only  nowadays 
coming  to  be  fully  appreciated  by  the  palae- 
ontologists themselves.  From  collectors  and 
specialists  they  are  becoming  not  only 
museum-makers,  but  so  far  also  artists,  not 
only  arranging  their  specimens  in  clear  evo- 
lutionary series,  like  the  horses  at  Yale  or 
the  elephants'  teeth  at  South  Kensington, 
or  setting  up  their  skeletons  in  living  atti- 
tudes, like  the  marvellous  group  of  Iguano- 
dons  which  are  the  glory  of  the  Brussels 
Museum,  but  becoming  also  sculptors,  and 
modelling  their  ancient  monsters  as  they 
must  actually  have  lived.  Nearly  a  couple 
of  generations  ago  this  was  tried,  as  notably 
for  the  Ichthyosaurs  and  Plesiosaurs  (Liassic 
fish-dragons  and  sw^an-dragons)  at  the  Crys- 
tal Palace,  where  to  this  day  there  are  some 
weird  survivals,  but  with  inaccuracies  which 
were  only  too  severely  criticized.  Now,  how- 
ever, the  magnificent  Central  Natural  History 
Museum  of  New  York  has  not  a  few  examples 
of  this  new  branch  of  the  animal  sculptor's 
art,  which  hardly  yield  in  vividness  and 
convincingness  to  the  life-like  triumphs  of 


^      EVIDENCES  OF  EVOLUTION        39 

the  best  of  museum  taxidermists.  Yet  even 
these  are  but  a  beginning;  as  the  evolutionary 
mode  of  presentment  increasingly  dominates 
our  collections,  as  already  in  the  "Phyletic 
Museum"  which  has  been  so  appropriately 
established  as  the  Haeckel  memorial  at  Jena, 
or  in  the  central  hall  of  the  Natural  History 
Museum  in  London,  our  galleries  will  in- 
creasingly develop  their  panoramic  renewal 
of  the  forms  of  life  throughout  their  evolution, 
and  will  thus  express  the  record  of  the 
palseontologist  as  a  wonderland  for  the  child 
— whose  continual  interest  in  strange  beasts, 
a  delight  thrilled  with  terror,  is  perhaps  itself 
a  survival  and  a  recapitulation  of  the  past 
mental  experience  of  our  race. 


CHAPTER  II 

EVIDENCES  OF  EVOLUTION  FROM  ANATOIVHST, 
EMBRYOLOGIST  AND  PHYSIOLOGIST 

Three  Foundations  of  the  Doctrine  of  Descent — Ho- 
mologies— New  Organs  from  Old — Classification — Vestigial 
Structures — The  Recapitulation  Doctrine.  Experi- 
mental Evolution — Direct  Evidence  of  Blood-relation- 
ship— Man  as  Transformist. 

Three  Foundations  of  the  Doctrine  of 
Descent. — The  general  theory  of  organic 
evolution — for  so  long  conveniently  called 
the  "doctrine  of  descent" — has  a  tripod 
basis. 

(a)  It  rests,  as  we  have  seen,  on  definitely 
''historical"  evidence — on  what  can  be  ac- 
tually proved  in  regard  to  ancestry.  Thus 
recent  discoveries  have  made  the  lineage  of 
the  elephant  convincingly  clear,  equalling,  if 
not  surpassing,  in  evidential  value  that  of 
the  horse  itself. 

(b)  It  rests  also  upon  anatomical  evidence, 
on  the  disclosure  of  structural  resemblances, 
often  beneath  a  mask  of  functional  differ- 
ences, which  are  in  many  cases  so  intimate, 
so  thoroughgoing,  so  detailed,  that  it  is  im- 
possible to  doubt  that  they  spell  affiliation. 

40 


EVIDENCES  OF  EVOLUTION         41 

(c)  It  rests  thirdly  upon  embryological 
evidence,  for  the  individual  development 
seems  almost  to  go  out  of  its  way  to  reveal 
the  evolution  of  the  race.  The  familiar  de- 
velopment of  frog-spawn  into  tadpoles  and 
froglings  is  in  some  respects  almost  startling 
in  its  recapitulation  of  the  evolution  of  the 
Amphibian  race  from  fish  ancestors — an  evo- 
lution vouched  for  by  the  data  of  palaeon- 
tology and  comparative  anatomy. 

Following  the  historical  order,  we  pass 
from  the  distributional  evidences  of  evo- 
lution— whether  horizontal  and  geographical, 
or  vertical  and  palseontographical — to  the 
anatomical  data.  These  are  of  three  kinds 
at  least:  (1)  there  is  the  recognition  of 
homologies,  i.  e.  of  deeply-rooted  structural 
and  developmental  similarities;  (2)  there  are 
the  facts  of  classification,  that  species  fades 
into  species,  that  genus  is  linked  to  genus, 
that  tentative  genealogical  trees  are  possible; 
and  (3)  there  is  the  occurrence  of  vestigial 
structures,  of  which  there  is  no  feasible  in- 
terpretation except  in  terms  of  past  history. 

Homologies. — When  two  or  more  struc- 
tures, organs  or  specialized  parts,  in  one  and 
the  same  organism,  or  in  several  organisms, 
show  a  deep  resemblance  in  their  architecture 
and  also  in  their  manner  of  development, 
they  are  said  to  be  homologous.    When  they 


42  EVOLUTION 

resemble  one  another  in  having  a  similar  use, 
in  discharging  the  same  function,  they  are 
said  to  be  analogous.  This  distinction  of  the 
two  kinds  of  likeness,  which  are  confused  in 
popular  thought  and  language,  is  of  far- 
reaching  importance.  The  discipline  of 
comparative  anatomy,  largely  by  help  of  the 
Platonic  idea  of  the  "archetype" — the  es- 
sential or  ideal  form  of  each  group  or  species 
— had  made  the  idea  of  homology  clear 
before  it  reached  its  evolutionist  interpre- 
tation; and  research  increasingly  showed 
that  if  classification  is  to  be  a  grouping  to- 
gether of  forms  that  are  deeply  alike,  it  must 
rest  on  a  recognition  of  homologies,  and  that 
a  grouping  according  to  analogical  resem- 
blances is  bound  to  be  fallacious. 

Aristotle  (384-322  B.  c.)  recognized  real 
kinship  when  he  ranked  whales  with  mam- 
mals, not  with  fishes;  and  bats  with  mammals, 
not  with  birds.  And  from  that  early  date 
till  now  the  successful  classifiers  of  animals 
or  of  plants  have  been  those  who  saw  clearly 
through  all  deceptive  suggestions  of  func-? 
tional  resemblance  (analogy),  and  got  down 
to  the  sure  foundation  of  structural  and 
developmental  resemblance  (homology). 

To  make  the  distinction  between  homol- 
ogies of  essential  form  and  mere  analogies 
of  use  more  concrete,  let  us  recall  the  three 


EVIDENCES  OF  EVOLUTION        43 

instances  of  Owen,  to  whom  it  owes  its  classic 
statement: — 

(1)  The  wing  of  a  bird  and  the  arm  of  a 
man;  they  are  both  fore-Hmbs,  with  funda- 
mentally the  same  structure  as  regards  bones 
and  muscles,  nerves  and  blood-vessels;  they 
are  homologous,  but  not  analogous. 

(2)  The  wing  of  a  bird  and  the  wing  of  a 
butterfly;  they  are  both  organs  of  true  flight, 
but  they  have  no  structural  or  developmental 
resemblance;  they  are  analogous,  but  not 
homologous. 

(3)  The  wing  of  a  bird  and  the  wing  of 
a  bat;  they  are  both  fore-limbs  of  similar 
structure  and  development;  they  are  both 
organs  of  true  flight;  they  are  at  once  ho- 
mologous and  analogous. 

Now,  the  evolutionary  suggestiveness  of 
homologies  is  indisputable.  If  we  take,  for 
instance,  a  series  of  fore-limbs  among  back- 
boned animals — the  arm  of  a  frog,  the  paddle 
of  a  turtle,  the  wing  of  a  bird,  the  fore-leg  of 
a  horse,  the  flipper  of  a  whale,  the  wing  of  a 
bat,  and  the  arm  of  man — we  find  detailed 
homology  not  only  as  regards  the  bones,  but 
as  regards  muscles,  nerves,  and  blood-vessels. 
Throughout  there  is  close  similarity  in  the 
fundamental  material  and  in  the  mode  of 
origin,  but  the  final  results  how  different! 
There  is  moulding  and  shaping  and  twisting 


44  EVOLUTION 

of  the  same  old  materials,  and — it  is  Nature's 
conjuring — there  is  something  new  every 
time.  But  the  facts  being  so,  it  is  very 
difficult  to  suggest  any  interpretation  except 
one — that  the  resemblance  is  due  to  blood- 
relationship.  As  Darwin  said:  "How  inex- 
plicable is  the  similar  pattern  of  the  hand  of 
a  man,  the  foot  of  a  dog,  the  wing  of  a  bat, 
the  flipper  of  a  seal,  on  the  doctrine  of  in- 
dependent acts  of  creation!  How  simply 
explained  on  the  principle  of  the  natural 
selection  of  successive  slight  variations 
in  the  diverging  descendants  from  a  single 
progenitor! " 

New  Organs  from  Old. — Another  set  of 
suggestive  facts  is  found  in  what  the  compara- 
tive anatomists  have  shown  in  regard  to 
many  of  the  structural  novelties  which  ap- 
pear at  point  after  point  in  the  animal  series, 
that  they  are  old  organs  in  a  new  guise.  The 
poison  gland  of  a  snake  is  usually  a  specializa- 
tion of  the  parotid  salivary  gland;  the  milk- 
glands  of  ordinary  mammals  are  specializa- 
tions of  the  sebaceous  glands  of  the  skin,  while 
those  of  the  egg-laying  duckmole  and  spiny 
ant-eater  are  nearer  the  sweat-gland  type; 
the  chain  of  three  minute  bones  in  the  mam- 
malian ear,  conveying  vibrations  from  the 
drum  to  the  inner  ear,  is  in  a  sense  quite  new, 
and  yet  its  links  were  forged  long  before  there 


EVIDENCES  OF  EVOLUTION        45 

were  any  mammals;  similarly,  the  Eusta- 
chian tube  which  runs  past  the  ear  to  the 
back  of  the  mouth  in  amphibians,  reptiles, 
birds  and  mammals  corresponds  to  the  first 
gill-cleft  or  spiracle  of  a  shark.  Begging 
the  question,  we  may  state  it  as  one  of  the 
laws  of  evolution  that  markedly  new  struc- 
tures have  often  arisen  from  the  transfor- 
mation of  old  structures  of  quite  different 
function. 

Classification. — Some  reckon  that  there 
are  over  a  million  different  species  of  living 
creatures,  and,  in  any  case,  there  are  many 
myriads.  Now  these  species  are,  in  many 
cases,  linked  together  by  varieties  which 
make  strict  severance  difficult.  They  are 
like  constellations,  well-defined  at  first  glance, 
which  on  closer  inspection  are  seen  to  be 
connected  by  outlying  members  with  ad- 
jacent constellations.  Moreover,  they  can 
be  rationally  arranged  in  genera,  orders, 
families  and  classes;  yet  between  these 
there  appear  not  a  few  remarkable  connect- 
ing links;  there  is  structural  progress  from 
the  unicellular  organisms  upwards  along 
various  lines  of  organization;  and  it  is 
possible  to  make  a  provisional  genealogical 
tree  which  is  becoming  less  and  less  shadowy 
every  year,  though  the  mutual  relations  of 
the  larger  branches  are  still  very  obscure. 


46  EVOLUTION 

A  practical  study  of  the  species  of  plants  and 
animals,  and  of  the  way  one  category  of 
classification  includes  those  beneath  it — 
classes,  orders;  orders,  families;  families, 
genera;  genera,  species;  species,  varieties; 
and  varieties,  individuals — gives  us  "an 
impression  of  affiliation"  which  we  do  not 
get  from  a  classification  of  rocks  or  other 
inanimate  objects.  It  is  impossible  not  to 
feel  in  biological  classification  the  suggestion 
of  pedigrees  and  heraldry. 

Vestigial  Structures. — Both  in  plants 
and  animals  it  is  common  to  find  minute  and 
more  or  less  useless  representatives  of  organs 
which  are  well  developed  and  functional  in 
related  forms.  It  is  impossible  for  us  now- 
adays to  keep  from  calling  these  structures 
vestigial  (a  better  term  than  rudimentary, 
which  should  be  kept  for  what  is  incipient), 
and  from  regarding  them  as  the  tell-tale 
evidences  of  remote  ancestry.  Darwin  com- 
pared them  to  the  unsounded  letters  in  many 
words,  such  as  the  "o"  in  leopard,  the  "b" 
in  doubt,  the  "g"  in  reign,  which  are  quite 
functionless,  but  tell  us  something  about  the 
history  of  these  words.  Every  one  is  famil- 
iar with  the  numerous  functionless  flaps  and 
buttons  in  clothing  w^hich  once  had  a  mean- 
ing they  have  now  lost.  Similar  "vesti- 
gial structures"   or   "survivals"   persist   in 


EVIDENCES  OF  EVOLUTION        47 

the    recesses    of    all    manner    of    venerable 
institutions. 

From  this  point  of  view  our  own  body  is  a 
veritable  museum  of  relics.  But  these  are 
not  all  equally  venerable.  In  the  first  place, 
there  are  antique  structures  which  are  present 
only  in  the  embryo,  not  normally  coming  to 
anything  in  the  adult,  as  is  the  case  with  all 
the  visceral  clefts  (or  gill-clefts)  except  the 
first,  which  survives  as  the  Eustachian  tube. 
In  the  second  place,  there  are  old-fashioned 
structures  which  persist  in  adult  life,  but  in 
much  disguised  form.  Thus  the  gill-arches, 
whose  primary  significance  (in  the  lower 
Vertebrates)  was  to  support  gills,  persist  in 
our  body,  almost  unrecognizably  transformed, 
in  the  skeletal  support  of  the  tongue  and  in 
the  framework  of  the  larynx.  In  the  third 
place,  there  are  vestigial  structures  in  a 
stricter  sense,  because  far  more  recent — ■ 
dwindling  residues  persistent  in  adult  life, 
but  either  functionless  or  relatively  unim- 
portant, such  as  the  minute  "third  eyelid" 
which  lies  in  the  median  angle  of  our  eye,  or 
the  muscles  of  the  ear,  which  in  occasional 
individuals  are  strong  enough  to  move  the 
trumpet,  or  the  vermiform  appendix  on  the 
large  intestine.  This  last  anachronism  seems 
not  merely  to  have  outlived  its  usefulness;  it 
often  costs  a  man  his  life.    It  is  "  like  an  idle 


48  EVOLUTION 

person  in  a  community,"  peculiarly  liable  to 
go  wrong  and  give  rise  to  serious  mischief. 
Indeed,  this  is  true  of  not  a  few  other  vestigial 
organs. 

There  is  no  lack  of  eloquent  examples  from 
the  animal  kingdom.  The  baleen  whale  has 
no  functional  teeth,  and  yet  it  has  the  usual 
two  sets — which  never  cut  the  gum.  Whales 
have  no  visible  hind-legs,  yet  many  show 
vestiges,  with  bones,  cartilages,  and  even 
unmoving  muscles,  which  are  buried  deep 
below  the  surface  and  absolutely  useless. 
Most  snakes  are  absolutely  limbless,  but  in 
the  boa  constrictor  and  some  of  its  relatives 
there  are  quite  distinct  hind-legs,  though 
these  are  so  diminutive  as  to  require  looking 
for,  even  on  a  big  specimen. 

The  Recapitulation  Doctrine. — The 
greatest  of  embryologists,  von  Baer  (1792- 
1876),  was  not  an  evolutionist,  for  reasons 
which  his  dates  in  part  explain;  yet  he  was 
one  of  the  first  to  make  clear  what  has  always 
been  eloquently  suggestive  of  evolution — 
the  remarkable  resemblance  between  the 
embryos  of  different  types  of  the  same  great 
group.  Thus,  if  we  take  the  higher  Verte- 
brates, viz.  reptiles,  birds  and  mammals, 
there  is  an  undeniable  resemblance  between 
their  embryonic  stages.  They  seem,  as  it 
were,  to  travel  for  a  considerable  distance 


EVIDENCES  OF  EVOLUTION        49 

along  the  same  road,  or  along  closely  parallel 
roads,  before  they  diverge,  each  on  its  own 
path  of  development. 

It  is  only  in  a  very  general  way  that  we  can 
accept  the  late  Professor  Milnes  Marshall's 
epigram,  that  the  individual  climbs  up  its 
own  genealogical  tree;  yet  there  is  no  doubt 
that  the  development  of  the  individual  is  in 
some  measure  interpretable  as  a  condensed 
recapitulation  of  the  presumed  racial  evolu- 
tion. There  is  no  doubt  that  in  many  cases 
the  developing  embryo  pursues  a  strangely 
circuitous  path  instead  of  progressing  straight 
towards  its  goal,  and  the  only  light  that  we 
can  throw  on  many  instances  of  this  circui- 
tousness — when  it  is  not  adaptive  to  the 
peculiar  conditions  of  development — is  the 
light  from  the  past.  The  living  hand  of  the 
past  is  upon  the  embryo,  constraining  it  to 
follow  the  old  route  of  its  race,  and  often 
reasserting  its  power  in  trivial  details,  even 
when  a  considerable  short-cut  has  been  made. 

Thus  in  the  development  of  every  reptile, 
bird  and  mammal  there  are  residues  of  gill- 
clefts,  sometimes  imperfectly  opening,  which 
have  no  respiratory  significance  whatsoever, 
which  can  hardly  be  said  to  be  of  any  use  at 
all,  except  that  the  first  one  becomes  the 
Eustachian  tube  connecting  the  ear  with  the 
back  of  the  mouth.     There  is  no  known  inter- 


50  EVOLUTION 

pretation  of  these  except  as  recapitulations  of 
the  respiratory  apparatus  of  remote  aquatic 
ancestors. 

Every  one  is  familiar  with  the  bony  flat- 
fishes, such  as  plaice,  flounder  and  sole,  which 
have  an  asymmetrical  body  flattened  from 
side  to  side.  They  rest  and  swim  on  their 
right  or  left  side,  which  is  unpigmented,  and 
both  eyes  are  on  the  upturned  pigmented 
side.  Now  these  markedly  asymmetrical 
fishes  begin  their  life  with  perfect  symmetry 
just  like  other  fishes.  They  retain  this  for 
some  considerable  time  and  live  near  the 
surface.  At  a  certain  stage  a  very  remark- 
able lop-sidedness  of  growth  and  alteration 
of  equilibrium  sets  in;  they  begin  to  sink 
towards  the  bottom,  the  eye  on  the  down- 
turned  side  travels  round,  or  even  in  part 
through,  the  margin  of  the  head;  in  short,  a 
metamorphosis  occurs.  Different  natural- 
ists may  read  different  meanings  into  the 
word  "recapitulate,"  but  in  some  sense  it  is 
surely  true  that  these  flat  fishes  recapitu- 
late in  their  early  development  the  form  of 
symmetrical  ancestors. 

We  have  already  referred  to  the  case  of  the 
baleen  whale,  which  has  two  sets  of  teeth  in 
embryonic  life.  They  never  cut  the  gum, 
they  are  absorbed  at  a  very  early  stage,  they 
are  not  of  the  slightest  use.     It  appears  to  us 


EVIDENCES  OF  EVOLUTION        51 

that  in  the  inheritance  of  the  baleen  whale 
there  must  be  definite  "representative  par- 
ticles" corresponding  to  the  typical  mam- 
malian dentition,  that  they  are  still  strong 
enough  to  insist  on  some  expression  in 
development,  and  that  so  far  as  teeth  are 
concerned  the  whalebone  whale  is,  therefore, 
recapitulating,  obviously  in  much  condensed 
form,  an  ancestral  condition. 

A  fish  has  a  two-chambered  heart,  with  an 
auricle  that  receives  impure  blood  from  the 
body  and  a  ventricle  that  drives  it  to  the  gills. 
In  amphibians  the  auricle  is  divided  length- 
wise by  a  partition,  so  that  the  heart  becomes 
three-chambered.  In  reptiles  the  ventricle 
is  partially  divided  by  a  similar  partition,  and 
this  becomes  complete  in  the  case  of  the 
crocodile.  In  birds  and  mammals  the  heart 
of  the  adult  is  four-chambered,  with  two 
auricles  and  two  ventricles.  But  when  we 
inquire  into  the  development  of  the  heart 
of  the  bird  or  of  the  mammal,  we  find  a  series 
of  stages  which  are  in  a  general  way  parallel 
to  the  historical  evolution  of  the  heart  as  we 
see  it  registered  in  the  successive  grades — 
fish,  amphibian  and  reptile.  The  same 
impression  is  to  be  gained  from  a  study  of 
the  development  of  the  brain,  the  skull,  the 
kidneys,  and  other  organs.  It  seems  to  us 
impossible  to  deny  that  there  is  in  the  stages 


52  EVOLUTION 

of  organogenesis  (the  development  of  organs) 
some  sort  of  repetition  of  the  stages  in  the 
evolution  of  organs.  The  embryo  of  a 
higher  Vertebrate  has  still  in  some  measure 
to  recapitulate  the  steps  taken  by  the  devel- 
oping embryo  of  a  lower  Vertebrate;  and 
though  we  may  say  that  this  is  an  architec- 
tural necessity,  that  the  end  could  be  reached 
in  no  other  way,  the  facts  seem  to  press  us 
to  go  further  and  say  that  something  in  the 
inheritance,  which  is  due  to  literal  blood- 
relationship,  compels  the  repetition. 

Professor  T.  H.  Morgan  states  the  case  as 
follows: — "The  most  fundamental  difference 
between  the  view  of  von  Baer  and  modern 
views  is  due  to  our  acceptation  of  the  theory 
of  evolution,  which  seems  to  make  it  possible 
to  get  a  deeper  insight  into  the  meaning  of 
the  repetition,  that  carries  us  far  ahead  of 
von  Baer's  position.  For  with  the  accept- 
ance of  this  doctrine  we  have  an  interpre- 
tation of  how  it  is  possible  for  the  embryonic 
stages  of  most  members  of  a  group  to  have 
the  same  form,  although  they  are  not 
identical.  There  has  been  a  continuous, 
although  divergent,  stream  of  living  ma- 
terial, carrying  along  with  it  the  sub- 
stance out  of  which  the  similar  embryonic 
forms  are  made.  As  the  stream  of  embry- 
onic material  divided  into  different  paths  it 


EVIDENCES  OF  EVOLUTION        53 

has  also  changed  many  of  the  details,  some- 
times even  all ;  but,  nevertheless,  it  has  often 
retained  the  same  general  method  of  devel- 
opment that  is  associated  with  its  particular 
composition.  We  find  the  likeness,  in  the 
sense  of  similarity  of  plan,  accounted  for  by 
the  inheritance  of  the  same  sort  of  substance; 
the  differences  in  the  development  must  be 
accounted  for  in  some  other  way." 

In  thinking  of  the  repetition  or  recapitula- 
tion there  are  two  distinct  ideas  to  be  kept 
in  mind.  On  the  one  hand,  each  stage  in 
embryonic  development  is,  as  Professor  His 
put  it  long  ago,  "the  physiological  conse- 
quence of  the  preceding  stage  and  the  neces- 
sary condition  for  the  following."  "If  the 
embryo  is  to  reach  the  complicated  end- 
forms,  it  must  pass,  step  by  step,  through 
the  simpler  ones."  On  the  other  hand,  the 
inheritance  of  a  living  creature  is,  in  some 
manner  that  we  cannot  image,  a  condensa- 
tion of  ancestral  initiatives  which  are  mate- 
rially represented  in  the  living  substance  and 
compel  the  developing  embryo  to  re-tread, 
to  some  extent  at  least,  the  path  taken  by 
the  embryos  of  its  ancestors. 

Let  us  take  the  particular  case  of  the 
notochord,  a  supporting  axial  rod,  present  for 
some  time  at  least  in  all  Vertebrate  embryos, 
and  always  arising  in  the  same  way  as  a  fold 


54  EVOLUTION 

along  the  dorsal  median  line  of  the  embry- 
onic gut.  In  a  few  old-fashioned  types,  such 
as  lancelet  and  lamprey,  there  is  no  backbone, 
but  the  notochord  persists  throughout  life. 
From  fishes  upwards  it  is  gradually  replaced 
in  development  by  the  backbone.  The  noto- 
chord does  not  become  the  backbone,  but  is 
replaced  by  it.  The  two  are  quite  different 
embryologically,  the  notochord  arising  from 
the  inner  germinal  layer  or  endoderm,  the 
backbone  arising,  like  the  rest  of  the  internal 
skeleton,  from  the  middle  germinal  layer  or 
mesoderm.  In  point  of  fact,  the  backbone 
develops  from  a  mesodermic  sheath  around 
the  notochord,  a  permanent  structure  around 
a  temporary  structure,  as  a  tall  tower  might 
be  built  around  an  internal  scaffolding  of 
wood.  Now,  what  is  the  relation  between  the 
more  primitive  axis  or  notochord  and  its 
more  effective  substitute  the  backbone,  seeing 
that  the  former  does  not  become  the  latter  .f^ 
In  his  interesting  theory  of  "the  substitution 
of  organs,"  Xleinenberg  suggested  that  the 
notochord  supplies  the  stimulus,  the  neces- 
sary developmental  condition,  for  the  forma- 
tion of  the  backbone  when  suitable  materials 
are  forthcoming.  Of  course  we  require  to 
know  more  precisely  how  the  old-fashioned 
structure  prepares  the  way  for  and  stimulates 
the  growth  of  its  future  substitute,  but  the 


EVIDENCES  OF  EVOLUTION        55 

general  idea  of  one  organ  leading  on  to  an- 
other is  suggestive.  It  is  consistent  with  our 
general  conception  of  development — that 
each  stage  supplies  the  necessary  condition 
for  the  next;  it  helps  us  to  understand  more 
clearly  how  new  structures,  too  incipient  to 
be  functional,  and  old  structures,  too  transi- 
tory to  be  of  direct  use,  may  persist;  in  short, 
it  makes  the  process  both  of  development 
and  of  evolution  more  intelligible.  But  to 
the  idea  of  the  architectural  utility  of  the 
notochord  as  a  piece  of  scaffolding,  we  must 
add,  unless  the  recapitulation  is  simply 
metaphorical,  the  idea  that  the  notochord  is 
laid  down  to-day  in  the  development  of  a 
higher  Vertebrate  because  of  a  continuity  of 
germinal  material  since  the  days  of  the  an- 
cestral forms  which  had  no  backbone  at  all. 
It  must  be  admitted  that  the  recapitulation 
doctrine  has  been  often  stated  in  somewhat 
crude  and  exaggerated  form,  so  that  many 
saving-clauses  are  necessary.  The  human 
embryo  is  never  like  a  little  fish  or  a  little 
reptile;  the  resemblance  is  between  embry- 
onic stages.  The  recapitulation  is  general, 
not  exact;  there  is  often  abbreviation  and  a 
masking  of  the  old  by  the  new.  On  the  one 
hand,  old-fashioned  features  may  drop  out, 
having  no  significance  either  in  embryonic, 
larval  or  adult  life;  on  the  other  hand,  many 


56  EVOLUTION 

new  features  have  been  added  on  as  adapta- 
tions to  novel  conditions.  The  recapitulation 
is  seen  more  in  the  stages  in  the  development 
of  organs  than  in  the  development  of  the 
organism  as  a  whole,  and  the  reason  for  this 
is  obviously  to  be  found  in  the  individuality 
or  specificity  of  every  creature.  Increased 
precision  of  embryological  work  discloses 
individual  characteristics  even  in  early  stages 
of  development;  indeed,  a  skilled  embryolo- 
gist  (exaggerating  a  little  in  his  turn)  has 
said  that  even  a  blind  man  could  distinguish 
embryos  of  the  duck  from  those  of  the  fowl 
as  early  as  the  second  or  third  day  of  in- 
cubation. The  developing  frog  is  in  many 
ways  like  a  developing  fish,  for  instance,  as 
regards  its  heart  and  circulation,  but  it  is 
none  the  less,  from  almost  the  very  outset,  an 
amphibian  and  nothing  else. 

It  must  also  be  frankly  stated  that  we  are 
apt  to  get  into  a  vicious  circle  in  arguing 
about  recapitulation.  We  infer  the  pedigree 
from  the  development,  and  then  say  that  the 
development  recapitulates  the  pedigree.  But 
this  is  not  quite  so  bad  as  it  seems,  since  no 
racial  history  or  phylogeny  is  worth  consid- 
ering for  a  moment  that  does  not  show 
the  anatomical  affiliation  of  actual  forms, 
whether  living  or  fossil,  and  embryological 
investigation  cannot  do  more  than  suggest 


EVIDENCES  OF  EVOLUTION        57 

clues.  Again,  we  consider  the  circuitous- 
ness  of  the  frog's  life-history  and  find  in  it  an 
evidence  of  the  reality  of  recapitulation.  We 
say  that  in  the  development  of  many  of  its 
organs  the  frog  repeats  steps  which  were 
taken  by  the  fish  stock  from  which  the  race 
of  Amphibians  sprang.  We  then  use  this  as 
one  of  "the  evidences  of  evolution" — which 
we  have  already  assumed.  But  the  fallacy 
here  is  simply  that  we  cannot  directly  demon- 
strate the  truth  of  the  doctrine  of  descent; 
we  can  only  bring  forward  facts  which  sug- 
gest it,  and  which  it  serves  to  interpret. 

When  all  is  said,  then,  there  remains  good 
reason  for  keeping  firm  hold  of  this  idea, 
which  was  first  clearly  stated  in  its  full  evo- 
lutionary importance  by  Haeckel,  first  in 
his  notable  "Generelle  Morphologic,"  and 
later  in  his  more  popular  treatises.  This  he 
termed  the  "fundamental  biogenetic  law" 
that  "Ontogeny,  or  the  development  of  the 
individual,  is  a  shortened  recapitulation  of 
phylogeny,  or  the  evolution  of  the  race." 

Even  apart  from  recapitulation,  we  must 
admit  the  suggestive  general  fact  that  the 
developing  organism  passes  through  a  series 
of  stages,  which  often  differ  from  one  another 
in  the  same  sort  of  way  as  related  species 
differ  from  one  another. 

Experimental  Evolution. — In  his  "Nova 


58  EVOLUTION 

Atlantis,"  that  far-sighted  Utopia  of  sci- 
ence which  has  already  been  so  largely 
realized,  Bacon  suggested  that  experiments 
should  be  set  agoing  in  order  to  discover  how 
far  surroundings  can  affect  and  transform 
living  creatures;  and  many  naturalists  have 
dreamed  of  and  pleaded  for  such  an  Institute 
of  Experimental  Evolution.  One  such  has 
lately  been  founded  in  the  United  States, 
the  precursor,  it  is  to  be  hoped,  of  many  in 
Europe.  "Since  Nature,"  said  Isidore 
Geoff roy  Saint-Hilaire,  "left  to  herself  never 
allows  us  to  witness  modifications  of  much 
magnitude  in  the  conditions  of  life,  it  is  clear 
that  only  one  way  is  open  to  us  if  we  wish  to 
perceive  such  modifications  and  to  examine 
their  effects  on  the  organism;  we  must  oblige 
Nature  to  perform  that  which  she  would  not 
spontaneously  accomplish."  Good  exposi- 
tions of  the  results  of  various  sets  of  experi- 
ments will  be  found  in  H.  De  Varigny's 
"Experimental  Evolution"  (1892),  and  more 
recently  in  T.  H.  Morgan's  "Experimental 
Zoology"  (1907);  and  we  cannot  here  do 
more  than  give  a  few  typical  illustrations. 
In  a  few  cases  it  has  been  found  possible 
to  induce  experimentally  what  may  be  called 
an  adaptive  response.  Thus  Professor  Poul- 
ton's  beautiful  experiments  on  the  pupae  of 
certain  butterflies  show  that  the  colour  of 


EVIDENCES  OF  EVOLUTION        59 

the  clirysalid  is  affected  by  the  colour  of  the 
surroundings,  which  operates  in  some  mys- 
terious way  through  the  skin.  When  the 
pupation  occurs  on  a  Hght  background  the 
chrysalids  are  hghter;  when  on  a  dark  back- 
ground the  chrysahds  are  darker.  This  is 
undoubtedly  an  advantageous  response,  for 
it  has  been  proved  experimentally  that  in 
natural  conditions  survival  depends  in  great 
part  on  the  inconspicuousness  of  the  pupae 
in  the  place  where  they  are  fastened. 

In  connection  with  experimentally  induced 
adaptive  responses  Professor  T.  H.  Morgan 
makes  an  important  note:  "It  is  remarkable 
how  rare  are  adaptive  structural  responses, 
when  we  recall  the  fact  that  adaptation  of 
the  organism  to  its  surroundings  is  one  of  its 
most  characteristic  properties.  The  poverty 
of  adaptive  structural  response  does  not 
encourage  one  to  look  to  external  agents  as 
having  brought  about  directly  the  structural 
adaptation  of  organisms  to  external  con- 
ditions, even  if  it  could  be  shown  that  such 
influences  are  inherited. " 

Many  naturalists  have  experimented  with 
the  pupse  of  butterflies  and  moths,  subjecting 
them,  for  instance,  to  unusual  conditions  of 
temperature,  and  many  ver^^  interesting  re- 
sults have  been  reached.  In  cases  where 
there  are  distinct  summer  and  winter  adult 


60  EVOLUTION 

forms,  the  pupa  which  should  give  rise  to 
the  former  may  be  made  to  give  rise  to  the 
latter,  or  the  pupa  may  be  affected  by  cold 
or  by  heat  so  that  what  emerges  resembles 
not  the  local  form  of  the  species,  but  a 
northern  or  southern  variety.  Perhaps  the 
most  important  general  result  from  our 
present  point  of  view  is  that  "the  differences 
effected  by  changes  in  the  environment  have 
been  shown  in  some  cases  to  resemble  the 
kind  of  differences  that  separate  species  from 
each  other."  This  is  suggestive  and  im- 
portant, though  it  does  not  by  any  means 
prove  that  species  have  arisen  in  this  way. 

Mr.  J.  T.  Cunningham  put  very  young 
flounders  in  an  aquarium  lighted  from  be- 
low, and  observed  that  as  they  underwent 
their  peculiar  metamorphosis  the  pigment 
first  disappeared  as  usual  from  the  down- 
turned  side,  and  then  (in  11  cases  out  of  13) 
reappeared  under  the  unusual  stimulus  of 
light  from  below.  This  shows  that  the  normal 
absence  of  pigment  on  the  down-turned  side 
of  a  flat-fish  is  due  to  the  absence  of  the  light- 
stimulus  in  each  individual  case. 

Some  forty  years  ago  Schmankewitsch 
made  a  study  of  a  natural  experiment  that 
occurred  in  a  salt  lagoon  which  was  divided 
by  a  dam  into  an  upper  and  a  lower  part,  the 
latter  the  Salter  of  the  two.    In  a  spring  flood 


EVIDENCES  OF  EVOLUTION        61 

in  1871  the  waters  of  the  upper  part  swept 
over  the  dam  and  reduced  the  sahnity  in 
the  lower  part.  Thereafter  great  numbers  of 
a  tiny  brine-shrimp,  Artemia  saKna,  were 
observed  in  the  lower  part,  having  been 
presumably  washed  in.  After  a  time  the  dam 
was  repaired,  the  water  gradually  regained 
its  great  salinity,  and  the  brine-shrimps  in 
the  course  of  their  rapid  generations  lost  the 
well-developed  caudal  fins  characteristic  of 
Artemia  salina  and  became  like  another 
form  without  caudal  fins,  Artemia  mil- 
hausenii.  Passing  from  observation  to  ex- 
periment, Schmankewitsch  found  that  grad- 
ual concentration  of  the  water  led  to  the 
replacement  of  typical  forms  of  Artemia 
salina  by  forms  lilve  Artemia  milhausenii, 
and  he  also  showed  that  if  the  forms  without 
caudal  fins  were  kept  in  brine  which  was 
gradually  diluted,  a  pair  of  conical  promi- 
nences, each  with  a  bristle,  appeared  after 
some  weeks  at  the  end  of  the  tail.  Schman- 
kewitsch did  not  regard  the  change  he 
observed  as  a  transformation  of  one  species 
into  another,  and  it  seems  fairly  clear  that 
there  is  no  species  Artemia  milhausenii. 
What  he  did  show  was  that  alterations  in  the 
salinity  of  the  water  are,  in  the  course  of 
generations,  followed  by  slight  changes  in  tlie 
form  of  the  tail.     Bateson  and  others  have 


62  EVOLUTION 

shown  that  there  is  great  variability  in  the 
character  of  the  tail  and  bristles  of  Artemia 
salina,  and  that  the  tailless  form  is  connected 
by  intermediate  stages  with  the  fully  tailed 
typical  form.  A  careful  discussion  of  this 
freguently  misstated  case  will  be  found  in 
Bateson's  "Materials  for  the  Study  of 
Variation"  (1894). 

Direct  Evidence  of  Blood  Relation- 
ship.— Various  workers — Friedenthal,  Uhlen- 
huth  and  Nuttall — have  brought  forward 
experimental  evidence  of  blood-relationship, 
and  this  in  the  most  complete  and  literal 
sense.  Friedenthal  points  out  that  when 
the  blood  of  a  horse  is  transfused  into  an  ass, 
that  of  a  hare  into  a  rabbit,  or  that  of  an 
orang  into  a  gibbon,  or  that  of  man  into  a 
chimpanzee,  there  is  a  harmonious  mingling 
of  the  two.  But  when  human  blood  is 
transfused  into  eel,  pigeon,  horse,  dog,  cat, 
lemur  or  "non-anthropoid"  ape,  there  is  no 
harmonious  mingling.  The  human  blood 
serum  behaves  in  a  hostile  way  to  the  other 
blood,  causing  great  disturbance,  marked, 
for  instance,  by  the  destruction  of  the  red 
blood  corpuscles.  The  difference  in  the  two 
sets  of  cases  is  that  in  the  first  the  organisms 
are  closely  related,  in  the  second  they  are  not. 

Another  form  of  the  same  kind  of  experi- 
ment is  given  by  Uhlenhuth  and  Nuttall. 


EVIDENCES  OF  EVOLUTION        63 

The  blood-serum  of  a  rabbit  which  has  had 
human  blood  injected  into  it  forms  a  precipi- 
tate with  human  blood.  It  forms  almost  as 
marked  a  precipitate  when  it  is  added  to  the 
blood  of  an  anthropoid  ape.  As  Schwalbe 
sums  up  in  the  recent  Darwin  centenary 
volume:  "The  reaction  to  the  blood  of  the 
lower  Eastern  monkeys  is  weaker,  that  to  the 
Western  monkeys  weaker  still;  indeed,  in 
this  last  case  there  is  only  a  slight  clouding 
after  a  considerable  time  and  no  actual 
precipitate.  The  blood  of  the  Lemuridse 
(Nuttall)  gives  no  reaction  or  an  extremely 
weak  one,  that  of  the  other  mammals  none 
whatever.  We  have  in  this  not  only  a  proof 
of  the  literal  blood-relationship  between  man 
and  apes,  but  the  degree  of  relationship  with 
the  different  main  groups  of  apes  can  be 
determined  beyond  possibility  of  mistake." 
Man  as  Transformist. — It  is  time,  how- 
ever, to  pass  from  the  laboratory  to  the  breed- 
ing-pen and  experimental  plot,  to  recall  the 
very  striking  transformations  that  man,  by 
selective  breeding,  has  effected  in  his  domesti- 
cated animals  and  cultivated  plants.  Dar- 
win pointed  to  what  has  taken  place  in  the 
case  of  sheep  and  cattle,  cabbages  and  apples, 
and  a  score  of  other  cases,  and  pressed  home 
the  question:  If  Man  has  been  instrumental 
in  fixing  all  these  varieties  in  a  short  time. 


64  EVOLUTION 

what  may  not  Nature  have  effected  in  a  very 
long  time? 

There  are  over  two  hundred  very  well- 
marked  breeds  of  domestic  pigeons,  and 
there  are  at  least  ten  that  would  be  ranked 
as  distinct  genera  if  they  occurred  wild;  yet 
there  is  very  strong  evidence  that  all  are 
scions  of  the  blue  rock-dove,  Columba  livia. 
In  the  same  way  there  is  very  strong  evi- 
dence that  all  the  breeds  of  poultry — Ham- 
burghs  and  Dorkings,  Bantams  and  Silk- 
fowl,  and  all  the  rest  of  them,  are  descended 
from  the  jungle-fowl,  Gallus  bankiva,  still 
found  wild  in  some  parts  of  India  and  the 
Malay  Islands.  Since  the  canary  was  in- 
troduced into  Europe  about  the  middle  of  the 
sixteenth  century,  over  a  dozen  very  dis- 
tinctive races  have  been  established;  and  of 
course  varieties  for  "the  fancy"  without  end. 

It  is  a  remarkable  fact  that,  in  spite  of 
the  accuracy,  assiduity  and  collecting  ac- 
quisitiveness which  characterize  botanical 
systematists,  we  know  very  little  that  is 
quite  certain  about  the  pedigrees  of  culti- 
vated plants.  As  De  Vries  says:  The  origin 
and  history  of  the  greater  part  of  our  garden 
flowers,  fruits  and  vegetables  are  obscure; 
we  see  them  as  they  are,  and  do  not  know 
whence  they  came.  The  original  habitat 
for  a  whole  genus  or  for  a  species  at  large  may 


EVIDENCES  OF  EVOLUTION        65 

be  known,  but  questions  as  to  the  origin  of 
the  single  forms  of  which  it  is  built  up  or- 
dinarily remain  unanswered." 

But  in  spite  of  obscurities  as  to  origin,  the 
evolution  of  cultivated  plants  is  still  going 
on  before  our  eyes.  Whether  we  visit  the 
nearest  country  flower-show,  or  admire  from 
enchanting  distance  Mr.  Burbank's  latest 
creations — the  "primus  berry,"  the  "phe- 
nomenal berry,"  the  "Bartlett  plum,"  the 
spineless  cactus,  and  the  rest,  or  see  the 
Mendelian  experimenters  positively  manipu- 
lating the  inheritances  of  our  cereals,  we 
cannot  doubt  that  we  are  in  the  presence  of 
evolution  in  actual  process. 

It  is  necessary,  however,  to  point  out  that 
the  results  of  Mendelian  experiments  have 
somewhat  modified  our  view  of  what  man  is 
able  to  achieve  in  the  way  of  establishing  new 
breeds.  In  many  cases  it  seems  as  if  he  were 
only  assisting  in  the  "unpacking"  of  the 
extremely  complex  inheritance  of  the  wild 
type.  It  may  seem  that  new  peculiarities 
are  emerging,  but  in  many  cases  what  is  being 
effected  is  a  process  of  analysis  and  of  selec- 
tion. There  seems  to  be  no  doubt,  for 
instance,  that  the  colour-varieties  of  the  do- 
mestic rabbit  are  but  analyzed  in  varying 
measure  and  mixture  from  that  beautiful 
synthesis  of  hues  which  we  see  in  the  wild 


66  EVOLUTION 

rabbit.  As  similar  analytical  varieties  prob- 
ably occur  in  Nature,  the  facts  of  domesti- 
cation may  retain  their  position  among  the 
"evidences  of  evolution,"  though  our  in- 
terpretation of  many  of  them  is  being  altered 
by  the  Mendelians. 

In  this  case,  and  throughout  all  considera- 
tion of  "evidences,"  it  must  be  remembered 
that  the  evolution  idea  cannot  be  logically 
demonstrated.  It  is  not  a  simple  induc- 
tion from  particulars,  thoroughly  as  particu- 
lars support  it.  It  is  a  way  of  looking  at  the 
becoming  of  things;  and  it  is  the  only  sci- 
entific modal  interpretation  that  has  been 
suggested.  It  is  a  formula  that  fits  the  facts, 
and  all  the  facts  it  fits  are  its  "evidences." 


CHAPTER  III 

GREAT  STEPS   IN  EVOLUTION 

Evolution  a  great  Succession  of  Achievements — The  Begin- 
nings —  Protoplasm  and  Organisms — Characteristic  Fea- 
tures of  Living  Creatures — Origins  among  the  Protozoa — 
The  Protists— Plants  and  Animals— The  Cell-Cycle— The 
Beginning  of  a  Body — Beginning  of  Death — The  Origin 
of  Sex — The  Beginnings  of  Brains — The  Beginnings  of 
Behaviour — Progress  along  many  Lines — The  Ascent  of 
Vertebrates — The  Ascent  of  Man — Evolution  as  Retro- 
gressive— Deterioration  and  Parasitism. 

Evolution  a  Great  Succession  of 
Achievements. — It  is  impossible  to  appre- 
ciate our  own  human  position  aright  unless 
we  see  it  in  the  light  of  history.  We  must 
think  of  the  distant  stone  ages — when  man 
made  weapons  of  chipped  flints  and  then  of 
polished  stone;  of  the  prehistoric  metal 
ages  that  followed — when  man  made  weapons 
and  utensils  of  copper,  of  bronze,  and  then 
of  iron;  and  of  the  gradual  growth  of  civil- 
ization along  many  lines.  We  are  so  famil- 
iar with  the  result  that  we  are  apt  not  to 
think  enough  of  the  long  succession  of  achieve- 
ments— each  a  great  event  in  human  history. 
It  is  one  of  the  uses  of  a  museum,  provided 
it  be  on  evolutionary  lines,  like  the  Pitt 

67 


68  EVOLUTION 

Rivers  Museum  at  Oxford,  to  give  us  de- 
tailed pictures  of  the  state  of  things  in  age 
after  age.  We  must  have  a  series  of  human 
skulls,  a  series  of  weapons — a  series  of  every- 
thing that  has  evolved. 

Similarly,  no  one  can  adequately  appre- 
ciate a  fullv-formed  creature,  whether  an 
oak  tree  or  the  bird  on  its  branches,  a  frog 
or  an  eel,  a  butterfly  or  a  starfish,  who  does 
not  know  the  stages  of  its  individual  develop- 
ment, from  the  apparent  simplicity  of  the 
fertilized  egg-cell  onwards.  Looking  down 
from  the  summit  of  a  pass  which  it  has  taken 
us  all  day  to  reach,  we  see  the  village  in  the 
valley  from  which  we  started  at  daybreak, 
and  it  seems  like  a  great  stone's-throw  off. 
The  dips  and  ascents,  turns  and  twists,  of 
our  path  are  all  lost  to  sight;  only  those  who 
have  walked  over  it  know  what  the  climb 
has  really  been.  So  it  is  w^ith  a  retrospect 
on  evolution. 

It  is  an  easy  thing  for  us  to  say  that  the 
world  of  life  we  see  around  us  to-day  has 
evolved;  with  equal  ease  our  grandparents 
said  that  it  had  been  created.  But  it  is 
incumbent  on  the  able-minded  to  give  to  this 
doctrine  of  descent  a  solid  body  of  fact,  so 
that  they  may  realize  something  of  the 
grandeur  and,  let  us  add,  of  the  difficulty  of 
the  proposition.     In  other  volumes  of  this 


GREAT  STEPS  IN  EVOLUTION      69 

series  the  student  will  be  helped  to  fill  in 
some  of  the  details  of  the  evolution  chart, 
thus  Dr.  Scott  deals  with  the  pedigree  of 
Plants,  Professor  Gamble  with  Animal  Life, 
Dr.  Keith  and  Mr.  Marett  between  them 
with  man;  what  we  propose  in  this  chapter 
is  to  indicate  in  a  general  way  a  few  of  the 
great  steps  in  Organic  Evolution. 

The  Beginnings. — Until  the  earth  cooled 
and  consolidated  it  was  quite  unfit  to  be  a 
home  of  life.  It  follows  that  at  some  un- 
certain, but  inconceivably  distant  date,  living 
creatures  appeared  on  the  scene.  The  ques- 
tion is  :  What  was  the  manner  of  their  be- 
coming upon  the  previously  tenantless  earth  .^^ 
Our  answer  must  be  that  we  do  not  know. 
But  to  obviate  worse  answers  we  may  submit 
two  or  three  suggestions. 

It  may  be  that  germs  of  life  came  to  our 
earth  embosomed  in  meteorites.  This  was 
the  suggestion  of  Richter,  Helmholtz  and 
Lord  Kelvin.  But  it  is  difficult  to  conceive 
of  anything  like  the  protoplasm  we  know 
surviving  transport  in  a  meteorite. 

Some  authorities  who  have  found  satisfac- 
tion in  the  meteorite- vehicle  theory  have  also 
suggested  that  life  is  as  old  as  matter.  It 
must  be  noted,  however,  that  the  life  we 
know  is  always  associated  with  highly  com- 
plex substances  known  as  proteids,   which 


70  EVOLUTION 

are   more   like   termini   than   beginnings  in 
material  evolution. 

It  may  be  that  what  we  call  "living'* 
evolved  in  Nature's  laboratory  from  what 
we  call  "not-living,"  for  though  prolonged 
experiments  have  led  biologists  to  adhere 
dogmatically  to  the  dictum  "omne  vivum  e 
vivo,"  this  is  not  inconsistent  with  supposing 
that  spontaneous  generation  occurred  in 
favourable  conditions  very  long  ago.  Ver- 
worn  has  elaborated  a  suggestion  due  to  the 
great  physiologist  Pfliiger  (1875),  that  the 
cyanogen  radical  (CN)  may  have  been  the 
starting-point  of  the  proteid  molecule  which 
is  the  essential  part  of  the  physical  basis  of 
life.  As  cyanogen  and  its  compounds  arise 
in  an  incandescent  heat  when  the  necessary 
nitrogenous  compounds  are  present,  they  may 
have  been  formed  while  the  earth  was  still 
aglow;  with  their  property  of  ready  decom- 
position they  were  forced  into  correlation 
with  various  other  compounds  likewise  due 
to  the  great  heat;  when  water  was  precipi- 
tated upon  the  earth  these  compounds  en- 
tered into  chemical  relations  with  the  water 
and  its  dissolved  salts  and  gases,  and  thus 
originated  extremely  labile,  very  simple,  un- 
differentiated living  substance,  which  per- 
haps fed,  as  Sir  Ray  Lankester  has  suggested, 
upon  "antecedent  steps  in  its  own  evolution." 


GREAT  STEPS  IN  EVOLUTION      71 

It  must  be  noted,  however,  (1)  that  al- 
though the  synthetic  chemist  can  now  manu- 
facture artificially  such  natural  organic  prod- 
ucts as  urea,  alcohol,  grape  sugar,  indigo, 
oxalic  acid,  tartaric  acid,  salicylic  acid  and 
caffeine,  he  has  not  yet  come  near  the  arti- 
ficial synthesis  of  proteids;  (2)  that  we  are 
at  a  loss  to  suggest  what,  in  Nature's  as  yet 
very  hypothetical  laboratory  of  chemical 
synthesis,  could  take  the  place  of  the  direc- 
tive chemist;  and  (3)  that  there  is  a  great 
gap  between  making  organic  matter  and 
making  an  organism. 

It  is  plain,  therefore,  that  the  doctrine  of 
the  origin  of  the  living  from  the  not-living 
cannot  be  held  at  present  with  a  clear  or 
easy  mind,  yet  we  must  admit  that  as  an 
hypothesis  it  is  in  harmony  with  the  general 
trend  of  evolutionary  theory.  If  facts  ac- 
cumulate which  make  the  hypothesis  a  ten- 
able interpretation,  it  will  not  in  any  way 
affect  the  dignity  and  value  of  living  crea- 
tures, nor  of  our  own  life.  If  the  dust  of  the 
earth  did  naturally  give  rise  to  living  crea- 
tures, if  they  are  in  a  real  sense  born  of  her 
and  the  sunshine,  then  the  whole  world  be- 
comes more  continuous  and  vital,  and  all  the 
inorganic  groaning  and  travailing  becomes 
more  intelligible. 

Protoplasm  and  Organisms. — If  we  whip 


72  EVOLUTION 

up  in  a  tumbler  some  white  of  egg,  some 
yolk  of  egg,  some  casein  from  milk,  and  so 
on,  we  have  got  a  mixture  of  proteids,  one 
excellent  to  feed  protoplasm  with,  but  we 
have  not  got  protoplasm  itself.  Our  tum- 
bler-mixture is  only  a  fortuitous  concourse 
of  proteids;  whereas  protoplasm  is  an  in- 
tegrate of  proteids,  perhaps  with  fats  and 
amyloids  as  well — a  fortunate  combination  of 
molecules  in  instable,  even  mobile,  yet  en- 
during equilibrium. 

It  is  probable  that  the  potency  of  living 
matter  is  in  part  an  expression  of  the  com- 
plex inter-relations  of  the  diverse  proteids 
and  other  substances  of  which  it  is  com- 
posed. No  single  substance  may  mean  very 
much,  but  in  combination  they  are  irresis- 
tible. Indeed  we  may  compare  protoplasm 
to  a  successful  firm  which  owes  its  success  to 
an  unusually  fortunate  combination  of  part- 
ners— of  inventive,  organizing,  administrat- 
ing, pushing,  competitive  and  other  geniuses ! 

But  there  is  something  more.  The  firm 
works  as  a  unity,  and  this  is  its  essential 
secret.  It  is  unified  from  within,  whether 
by  a  common  purpose,  or  by  the  predomi- 
nant will  of  its  leading  partners,  or  by  some- 
thing of  both.  And  the  organism  has  like- 
wise its  secret,  its  internal  unity,  which  we 
are  still  far  from  understanding. 


GREAT  STEPS  IN  EVOLUTION      73 

Characteristic  Features  of  Living 
Creatures. — The  chemists  tell  us  that  the 
physical  basis  of  life  always  includes  pro- 
teids  and  similar  highly  complex  substances, 
and  that  the  process  of  living  involves  an 
intricate  series  of  combustions  and  fermen- 
tations and  reconstructions,  many  of  which 
can  be  imitated  outside  the  body  altogether 
and  expressed  in  chemical  formulae.  On  the 
other  hand  we  cannot  give  a  chemical  de- 
scription of  any  complete  vital  function,  or 
of  any  activity  of  the  living  creature  as  a 
whole — and  unless,  as  the  Germans  say,  we 
throw  away  the  baby  with  the  bath,  we  can- 
not ignore  the  most  salient  fact,  that  all  the 
manifold  chemical  processes  are  correlated 
and  controlled  in  a  unified  behaviour,  in  a 
purposive  agency.  Even  the  amoeba  is  no 
fool. 

The  physicists  tell  us  that  the  living  crea- 
ture resembles  some  wonderful  kind  of  en- 
gine; it  is  a  material  system  adapted  to 
transform  matter  and  energy;  and  it  illus- 
trates in  its  living  a  number  of  well-known 
physical  phenomena,  of  surface-tension,  of 
diffusion,  of  elasticity,  of  hydrostatics,  of 
thermodynamics,  of  electricity,  and  so  on. 
At  the  same  time  it  has  to  be  admitted  that 
not  even  the  simplest  vital  activity,  such  as 
the  passage  of  digested  food  from  the  all- 


74  EVOLUTION 

mentary  canal  into  the  blood-vessels,  can  be 
completely  described  in  terms  of  physical 
formulse.  The  fact  is  that  when  we  add  up 
the  components  revealed  by  chemical  and 
physical  analysis,  they  do  not  amount  to 
the  whole  resultant  which  we  see  in  a  vital 
action,  even  of  a  simple  sort. 

It  is  indeed  profitable  to  compare  a  living 
creature  to  a  machine,  and  a  fertile  method 
of  discovery  to  press  this  comparison  to  its 
hardest.  Yet  the  living  organism  differs 
from  any  machine  in  its  greater  efficiency; 
and  especially  in  this,  that  the  transfer  of 
energy  into  it  is  attended  with  effects  con- 
ducive to  further  transfer  and  retardative 
of  dissipation.  Again  in  this,  that  it  is  a 
self-stoking,  self-repairing,  self-preservative, 
self-adjusting,  self-increasing,  self-repro- 
ducing engine!  And  this  also  must  be  re- 
membered in  comparing  a  living  creature 
and  a  machine,  that  the  latter  is  no  ordinary 
sample  of  the  inorganic  world.  It  is  an 
elaborated  tool,  an  extended  hand,  and  has 
inside  of  it  a  human  thought.  It  is  because 
of  these  qualities  that  highly  complex  ma- 
chines come  to  be  so  like  organisms.  But 
no  machine  profits  by  experience,  nor  trades 
with  time  as  organisms  do.  Therefore  it  is 
that  the  formulae  that  serve  to  describe  the 
activity  of  a  machine  will  not  suffice  for 


GREAT  STEPS  IN  EVOLUTION      75 

living  creatures  which  demand  an  historical 
explanation. 

When  we  leave  the  chemical  and  physical 
standpoint,  and  look  at  the  living  creature  as 
biologists,  we  recognize  four  chief  character- 
istics— growth,  cyclical  development,  effec- 
tive response,  and  unified  behaviour.  The 
living  creature  grows  after  a  fashion  all  its 
own,  not  as  a  rolling  snowball,  by  mere 
accretion,  but  by  a  unifying  incorporation; 
not  even  as  a  crystal  grows,  at  the  expense 
of  dissolved  material  chemically  the  same  as 
itself,  but  at  the  expense  of  material  different 
from  itself.  Again,  it  has  a  cyclical  develop- 
ment, from  egg-cell  to  seedling,  from  seed- 
ling to  beanstalk;  from  egg-cell  to  tadpole, 
from  tadpole  to  frog;  it  shows  an  orderly, 
correlated,  regulated  succession  of  events, 
which  leads  from  apparent  simplicity  to 
obvious  complexity;  but,  as  Huxley  puts  it, 
"no  sooner  has  the  edifice,  reared  with  such 
exact  elaboration,  attained  completeness, 
than  it  begins  to  crumble."  Inanimate 
objects  have  a  certain  power  of  response  to 
external  stimuli,  as  a  piece  of  potassium 
shows  when  thrown  on  a  basin  of  water,  but 
the  responses  of  a  living  creature  in  normal 
surroundings  are  effective,  self-preservative, 
usually  making  for  betterment.  Lastly,  the 
living  creature  has  a  persistent  unified  be- 


76  EVOLUTION 

haviour,  a  power  of  profiting  by  experience, 
a  creative  capacity  as  a  genuine  agent. 

Origins  among  the  Protozoa. — It  is  well 
over  two  centuries  since  the  Dutch  micro- 
scopist,  Leeuwenhoek,  exhibited  to  the  Royal 
Society  of  London  some  of  those  unicellular 
animals  or  animalcules  which  we  now  call 
Protozoa — the  Fellows  present  signing  an 
affidavit  that  they  had  really  seen  the  mi- 
nute creatures.  This  was  the  beginning  of  a 
study  which  has  been  extraordinarily  fertile 
in  itself  and  in  its  bearing  on  other  lines  of 
research.  As  has  become  so  emphatic  re- 
cently, the  study  is  one  of  enormous  practi- 
cal importance  to  man,  since  some  of  the 
most  terrible  diseases,  such  as  malaria  and 
sleeping  sickness,  are  due  to  Protozoa,  but 
the  study  is  also  of  fundamental  theoretical 
importance.  For  the  Protozoa  give  us,  so 
to  speak,  a  natural  analysis  of  the  elements 
which  compose  the  higher  animals;  the 
phases  of  their  life-cycles  are  sometimes 
echoed  in  the  cellular  variations  of  man  him- 
self; a  few  of  them  seem  to  linger  in  a  state 
of  relative  simplicity,  approximating  to  that 
which  must  have  characterized  the  true 
Protozoa,  or  first  animals;  they  are,  as  it 
were,  permanent  germ-cells  which  never 
get  beyond  the  ovum  and  sperm  stage;  and 
they  show  us  the  beginnings  of  division  of 


GREAT  STEPS  IN  EVOLUTION      77 

labour  and  its  structural  aspect  which  we  call 
differentiation,  the  beginnings  of  sex  and  of 
reproduction,  the  beginnings  of  a  body  and 
of  death.  "Protozoology,"  as  it  is  quaintly 
called  nowadays,  is  a  fascinating  study  in 
origins. 

The  Protists. — It  is  useful  to  retain 
Haeckel's  term  "Protists"  for  those  simplest 
of  all  living  creatures,  which  lie  at  the  base  of 
the  V-shaped  tree  of  life,  showing  no  definite 
bias  towards  distinctively  plant  or  distinct- 
ively animal  characteristics.  How  far  re- 
moved even  these  simplest  of  the  simple  may 
be  from  the  first  living  creatures  we  do  not 
know,  but  they  have  remained,  as  it  were, 
in  chronic  indecision,  neither  clearly  plants 
nor  animals.  In  studying  them  we  are 
brought  face  to  face  with  one  of  the  great 
steps  in  evolution,  and  one  of  the  earliest — a 
dichotomy,  like  many  other  great  steps — the 
parting  of  the  ways  between  plants  and 
animals. 

Plants  and  Animals. — We  have  all  grown 
up  with  our  minds  coloured  by  the  childish 
game  of  "Animal,  Vegetable  or  Mineral.^" 
and  in  too  many  schools  they  still  teach  that 
there  are  three  kingdoms  of  Nature.  But 
this  is  a  surviving  error  of  the  alchemists, 
continued  by  the  early  encyclopaedists  of 
nature,  but  broken  down  by  Linnaeus,  who 


78  EVOLUTION 

clearly  discerned  that  there  are  only  two: 
the  living  and  the  non-living,  the  truly  organ- 
ized and  the  merely  aggregated.  Hence  in 
his  immortal  "System  of  Nature"  he  unites 
Animalia  and  Vegetabilia  as  Organisata,  and 
separates  Mineralia  as  Conserta.  True,  he 
falls  somewhat  from  this  again,  witness  his 
famous,  but  very  fallacious,  aphorism — 
'* Minerals  grov/;  Plants  grow  and  live; 
Animals  grow,  live  and  feel";  yet  the  great 
distinction  of  life  is  not  lost  sight  of. 

Since  Claude  Bernard,  more  than  a  genera- 
tion ago,  wrote  his  famous  book,  "Pheno- 
menes  de  la  vie  communs  aux  animaux  et 
aux  vegetaux,"  it  has  been  recognized  that 
the  beech-tree  feeds  and  grows,  digests  and 
breathes,  as  really  as  does  the  squirrel  on  its 
branches;  that  in  regard  to  none  of  the  main 
functions  (except  excretion,  which  plants 
have  little  of)  is  there  any  essential  differ- 
ence; and  that  plants,  though  for  the  most 
part,  as  it  were,  asleep,  give  many  striking 
illustrations  of  their  power  of  movement  and 
their  irritability. 

We  must  remember  also  that  plants  and 
animals  are  alike  in  fundamental  architec- 
ture, being  built  up  of  cells  and  various  mod- 
ifications of  cells.  And  there  is  a  third  deep 
resemblance,  that  when  we  trace  a  beech- 
tree  or  a  squirrel  back  to  its  individual  begin- 


GREAT  STEPS  IN  EVOLUTION      79 

ning  we  find  a  fertilized  egg-cell,  which 
divides  and  re-divides,  the  body  of  the  plant 
or  animal  being  built  up  by  continued  divis- 
ion, arrangement  and  differentiation  of  cells. 
But  important  as  these  resemblances  be- 
tween plants  and  animals  are,  the  divergence 
is  very  profound  and  expresses  one  of  the 
great  cleavages  in  evolution. 

It  came  about  through  the  invention  of 
chlorophyll  by  some  Protists — a  chemical 
and  physiological  achievement  of  the  highest 
magnitude,  which  made  the  life  of  plants 
possible,  and,  through  them,  that  of  animals 
and  man.  In  the  complex  "photo-synthesis" 
by  which  plants  build  up  complex  carbon- 
compounds  from  the  raw  materials  of  water, 
air  and  earth,  chlorophyll  plays  an  indispen- 
sable part.  The  still  widely  prevalent  ig- 
norance of  this  fundamental  process  of  the 
living  world  is  perhaps  the  greatest  example 
of  the  slowness  with  which  the  discoveries 
of  science  become  generally  recognized. 

Most  plants  derive  the  carbon  they  require 
from  the  carbon  dioxide  of  the  air,  while 
only  a  few  (green)  animals  have  this  power; 
all  the  others  depend  for  their  carbon  supplies 
on  the  sugar,  starch,  fat,  etc.,  already  made 
by  other  animals  or  by  plants.  As  regards 
nitrogen,  most  plants  take  this  from  nitrates 
and  the  like,  absorbed  along  with  water  by 


80  EVOLUTION 

the  roots;  whereas  animals  obtain  their 
nitrogenous  supplies  from  the  complex  pro- 
teids  formed  within  other  organisms.  Most 
plants,  therefore,  feed  at  a  lower  chemical 
level  than  do  animals,  and  it  is  characteristic 
of  them  that,  in  the  reduction  of  carbon 
dioxide  and  in  the  manufacture  of  starch 
and  proteids,  the  kinetic  energy  of  sunlight 
is  transformed  by  the  living  matter  into  the 
potential  chemical  energy  of  complex  food- 
stuffs. Animals,  on  the  other  hand,  get  their 
food  ready-made;  they  take  the  pounds 
which  plants  have,  as  it  were,  accumulated 
in  pence,  and  they  spend  them.  For  it  is 
characteristic  of  animals  that  they  explo- 
sively convert  the  potential  chemical  energy 
of  food-stuffs  into  the  kinetic  energy  of  loco- 
motion and  other  activities.  In  short,  the 
great  distinction — an  average  one  at  best — • 
is  that  most  animals  are  more  active  than 
most  plants. 

Changing  the  point  of  view  a  little,  we  may 
notice  that,  because  of  their  mode  of  nu- 
trition, typical  animals  are  bound  to  be 
active  and  locomotor  either  in  whole  or  in 
part.  Similarly  we  may  say  that  the  plant- 
cell,  by  shutting  itself  up  in  a  wall  of  cellulose, 
instead  of  fully  oxidizing  this  substance, 
and  perhaps  also  by  less  efficient  elimination 
of  nitrogenous  waste,  doomed  itself  to  fixity 


GREAT  STEPS  IN  EVOLUTION      81 

and  to  sleep.  Yet  something  of  the  animal 
impulse  of  the  ancestral  Protists  lingers  in 
the  plant,  and  something  of  the  vegetative 
tendency  of  the  ancestral  Protist  lingers  in 
the  animal. 

We  have  dwelt  for  a  little  on  this  ele- 
mentary question  of  the  distinctions  between 
plants  and  animals,  because  it  is  the  funda- 
mental illustration  of  a  bifurcation  that  has 
recurred  many  times  in  the  evolution  of 
living  creatures.  Living  implies  two  great ^ 
processes — of  repairing  and  wasting,  of  build-  ; 
ing  up  and  breaking  down,  of  construction 
and  disruption — more  technically,  of  ana- 
bolism  and  katabolism.  Given  a  typical 
plant  and  animal  of  equal  weight,  both  living 
normally,  we  might  safely  say  that  the 
animal  lives  much  more  nearly  up  to  its 
income  than  the  plant  does.  If  we  express 
the  vital  ratio  of  anabolism  to  katabolism 

as  —  for  the  plant  and  -  for  the  animal,  we 

may  safely  say  that  —  is  always  much  greater 

ii. 

than   —      In    the   plant   the   numerator   is 

always  large  in  proportion  to  the  denomi- 
nator. In  the  animal  there  is  a  relative 
preponderance  of  katabolic  processes.    Thus 


82  EVOLUTION 

at  point  after  point  in  the  history  of  organ- 
isms the  evolving  Proteus  has  had  to  face 
the  alternatives  of  two  possible  regimes 
precisely  corresponding  to  the  alternative 
between  Plant  and  Animal  in  the  earliest 
days. 

The  Cell-Cycle. — When  we  take  a  sur- 
vey of  a  representative  set  of  unicellular 
organisms — amoebae,  foraminifers,  sun-ani- 
malcules, infusorians,  gregarines,  and  simple 
algse  and  fungi  as  well,  we  reach,  almost  by 
inspection,  a  rough  and  ready  tripartite 
classification  into  very  active  and  very  pas- 
sive forms,  with  amoeboid  forms  midway.  At 
one  extreme  are  the  highly  active  infusorians, 
such  as  the  widely  diffused  free-living  slipper- 
animalcules,  or  the  widely  diffused  parasitic 
trypanosomes  (one  of  which  causes  sleeping- 
sickness);  at  the  opposite  extreme  are 
quiescent  forms,  in  which  the  life  seems  to 
sleep;  between  the  two  the  amoeboid  forms 
have  evolved  along  a  via  media — a  com- 
promise between  extreme  activity  and  ex- 
treme passivity. 

If  we  go  deeper  than  mere  inspection  and 
study  the  life-history  of  the  very  simplest 
forms,  such  as  some  of  the  primitive  Proteo- 
myxa  and  Myxomycetes,  we  get  a  new  light 
on  our  classification.  For  in  these  life- 
histories  we  find,  for  instance,  that  amoeboid 


GREAT  STEPS  IN  EVOLUTION      83 

forms  become  encysted,  that  the  encysted 
stage  gives  rise  to  active  flagellate  spores, 
and  that  these  sink  down  again  into  amoebae. 
The  three  chapters  in  the  life-history  of  the 
simplest  forms  are,  as  it  were,  prophecies  of 
each  of  the  three  groups — Infusorians,  Rhizo- 
pods,  and  Gregarines.  In  other  words,  the 
most  primitive  organisms  pass  through  a 
cycle  of  three  phases,  one  of  which  is  ac- 
cented by  each  of  the  three  main  groups  of 
Protozoa.  And  while  each  main  group  is 
characterized  by  one  dominant  phase  of 
cell-life — flagellate,  amoeboid  or  encysted — 
there  are  often  transient  hints  of  other  phases. 
An  infusorian  may  have  its  encysted  chapter, 
a  gregarine  its  amoeboid  stage,  and  a  rhizopod 
may  begin  as  a  mobile  flagellate  spore;  for 
each  group,  while  accenting  one  phase  of 
the  cycle,  retains  reminiscences  of  the  others. 
The  conviction  that  the  triple  division 
really  means  much,  grows  stronger  when  we 
pass  from  the  unicellulars  to  the  cells  that 
compose  the  higher  animals.  For  they,  too, 
may  be  rationally  classified  along  the  three 
great  lines.  There  are  active  ciliated  or 
flagellate  cells  in  most  animal  types — the 
flagellate  cells  of  sponges,  the  "flame-cells" 
of  the  lower  worms,  the  ciliated  epithelium 
lining  our  air-passages,  being  three  familiar 
illustrations.     The   white   blood   corpuscles 


84  EVOLUTION 

are  obviously  comparable  to  amoebae.  Pas- 
sive encysted  cells  are  illustrated  in  some 
forms  of  connective,  skeletal  and  fatty  tissue. 
Thus  the  physiological  classification  of  the 
Protozoa  is  verified  in  the  histology  of  the 
higher  animals,  and  is  further  corroborated 
in  the  study  of  their  diseases.  In  a  certain 
kind  of  "sore  throat"  the  ciliated  cells  of  the 
windpipe  sink  into  an  amoeboid  phase,  echo- 
ing a  normal  change  in  the  life-history  of  the 
simplest  Protists.  The  young  ovum  is  often 
amoeboid,  the  mature  ovum  is  encysted;  the 
typical  spermatozoon  is  flagellate,  but  there 
are  some  exceptional  amoeboid  forms.  Fi- 
nally, the  same  cell-cycle  is  not  only  recog- 
nizable in  the  reproduction  of  the  lower 
plants,  but  is  plain  in  the  higher  cryptogam, 
and  vestigial  in  the  flower.  And  the  deep 
significance  and  historical  importance  of 
the  lines  of  differentiation  indicated  by  the 
cell-cycle  become  more  evident  still  when  we 
recognize  that  the  three  phases  correspond 
to  the  three  possibilities  of  relatively  pre- 
ponderant anabolism,  relatively  predom- 
inant katabolism,  and  a  compromise  between 
these  two. 

The  Beginning  of  a  Body. — The  simplest 
organisms  are  single  cells  physiologically 
complete  in  themselves;  they  leave  off  where 
higher  creatures  begin,  that  is  to  say,  in  a 


GREAT  STEPS  IN  EVOLUTION      85 

unicellular  state;  they  do  not  form  "bodies." 
Here  we  have  perhaps  the  greatest  gap  and 
the  greatest  step  in  organic  nature,  that 
between  single-celled  and  many-celled  organ- 
isms. It  is  very  interesting  to  inquire  into 
the  beginning  of  a  "  body."  What  are  the 
possibilities.^ 

We  know  of  some  simple  units  that  have  a 
habit  of  coalescing  into  composite  masses,  of 
others  in  which  the  nucleus  divides  over  and 
over  again  within  the  cell  so  that  multi- 
nucleate organisms  are  formed,  and  of  others 
again  that  break  their  definition,  and  do  their 
best  to  get  beyond  the  unicellular  state,  by 
forming  loose  colonies.  It  was  probably  in 
the  third  of  these  ways  that  body-making 
began.  Certain  simple  organisms,  unable 
fully  to  complete  that  division  into  two  or 
more  separate  units  which  normally  occurs 
at  the  limit  of  growth,  bridged  what  Agassiz 
called  "the  greatest  gulf  in  organic  nature." 
It  was  perhaps  through  some  weakness  that 
the  daughter-units,  formed  by  division  of 
the  mother-cell,  remained  associated,  instead 
of  drifting  apart  in  individual  completeness. 
But  out  of  this  weakness — if  weakness — 
strength  arose,  the  strength  of  animals 
with  a  body. 

Beginning  of  Death. — In  a  startling 
phrase — the  immortality  of  the  Protozoa — 


86  EVOLUTION 

Weismann  called  attention  to  the  fact  that 
unicellular  organisms  are  not  subject  to 
natural  death  in  the  same  degree  as  higher 
animals  are.  They  may  be  killed,  of  course, 
in  many  ways,  but  they  do  not  normally  die. 
Even  against  microbic  infection  many  of 
them  seem  proof;  they  digest  the  virulent 
intruders,  as  do  the  phagocytes  which  form 
our  body-guard.  But  the  point  is,  that  in 
natural  conditions,  where  inter-crossing,  for 
instance,  is  readily  feasible,  they  appear  to 
be  exempt  from  that  natural  death  which 
in  the  higher  organisms  is  due  to  the  slow 
mounting-up  of  physiological  arrears. 

How  is  it  that  these  simple  pioneer  organ- 
isms are  exempt  from  the  penalty  all  other 
flesh  is  heir  to.^^  The  answer  is  twofold.  On 
the  one  hand,  being  relatively  very  simple, 
in  a  strict  sense  without  a  "body" — they  are 
able  to  sustain  with  persistent  success  the 
vital  equation  between  waste  and  repair.  On 
the  other  hand,  their  common  mode  of  repro- 
duction, by  dividing  into  two  or  more  units, 
is  inexpensive  and  not  attended  with  any  loss 
of  life.  For  although  the  individual  A  dis- 
appears in  giving  rise  to  B  and  C,  its  daugh- 
ter-cells, we  can  hardly  speak  of  death  when 
there  is  nothing  left  to  bury.  On  the  one 
hand,  we  reach  the  idea  that  death  was  the 
price  paid  for  a  body;  on  the  other  hand, 


GREAT  STEPS  IN  EVOLUTION      87 

we  see  that  in  the  simplest  forms  of  hfe  im- 
mortahty  has  not  even  yet  been  pawned  for 
love. 

The  Origin  of  Sex. — In  many  of  the  uni- 
cellular organisms  there  is  a  kind  of  sexual 
reproduction,  in  the  sense  that  two  cells  fuse 
to  become  one,  just  as  ovum  and  sperma- 
tozoon do  in  higher  creatures.  In  many 
cases,  moreover,  the  two  cells  which  fuse  are 
dimorphic,  as  is  well  illustrated  in  the  bell- 
animalcule,  Vorticella,  where  a  small,  active, 
free-swimming  (we  may  say  male)  cell  unites 
with  a  fixed  individual  of  full  size,  which 
may  be  called  female.  This  is  one  line  of 
approach  to  the  origin  of  sex,  and  it  may  be 
noted  that  the  male  and  female  cells  illus- 
trate the  antithesis  we  have  already  discussed 
between  relatively  more  anabolic  and  rela- 
tively more  katabolic  types. 

The  next  stage  in  the  problem  is  to  account 
for  the  familiar  fact  that  in  almost  all 
organisms  with  bodies  there  are  special 
reproductive  cells,  or  germ-cells — ova  and 
spermatozoa — quite  distinct  from  the  or- 
dinary body-cells.  This  is  an  economical 
improvement  on  the  method  of  starting  a 
new  life  by  a  sexual  over-growth  or  by  the 
liberation  of  buds.  Moreover,  the  peculiarity 
of  true  germ-cells  is  that  they  do  not  share  in 
building   up   the    "body,"    and   that   they 


88  EVOLUTION 

retain  an  organization  continuous  in  quality 
with  the  original  germ-cell  from  which  the 
parent  arose.  They  are  thus  not  very  liable 
to  be  tainted  by  the  mishaps  which  may  befall 
the  "body"  which  bears  them.  And  again, 
in  the  life-history  of  the  germ-cells,  and  in 
the  mingling  of  two  of  them  of  different 
experiences  in  fertilization,  there  is  appar- 
ently opportunity  for  new  organic  permuta- 
tions and  combinations  —  variations  in  short. 
Perhaps  there  is  some  subtler  advantage 
still  in  the  process  which  ensures  that  each 
new  life  usually  begins  in  a  unification  of 
two  inheritances. 

The  third  aspect  of  the  problem  is  that 
most  multicellular  organisms  are  males  or 
females.  The  former  liberate  male  elements, 
which  are  usually  actively  motile;  the  latter 
form,  and  usually  liberate,  more  passive  egg- 
cells  or  ova.  In  the  lower  reaches  of  the 
animal  kingdom  there  is  seldom  much  differ- 
ence between  males  and  females;  indeed,  it  is 
often  impossible  to  distinguish  the  two  sexes 
without  a  microscopic  examination  of  the 
reproductive  organs.  It  is  obviously  at  this 
level,  and  not  with  the  highly  specialized  sex 
dimorphism  of  peacock  and  peahen,  ruff  and 
reeve,  lion  and  lioness,  man  and  woman, 
that  the  problem  should  be  first  studied. 

The   problem   is   partly   solved   by   con- 


GREAT  STEPS  IN  EVOLUTION      89 

^sidering  the  simplest  expressions  of  the  sex- 
difference,  as  we  see  it,  for  instance,  in 
Volvox,  an  interesting  colonial  Infusorian, 
which  well  illustrates  a  body  in  the  making. 
It  is  a  beautiful  rolling  ball  of  ciliated  cells, 
and  these  component  units  are  connected 
by  protoplasmic  bridges.  From  the  ball  of 
cells  reproductive  units  are  sometimes  set 
adrift,  which  divide  to  form  other  colonies 
without  more  ado.  But  in  other  conditions, 
when  nutrition  is  checked,  a  less  direct  mood 
of  reproduction  occurs.  Some  of  the  cells 
in  the  ball  become  large,  well-fed  elements 
■ — the  ova;  others,  less  anabolic,  fade  from 
green  to  yellow,  divide  and  re-divide  into 
many  minute  units — the  spermatozoa.  The 
large  cells  of  one  colony  are  fertilized  by 
the  small  cells  from  another.  Here  we  see 
the  formation  of  dimorphic  reproductive 
cells  in  different  parts  of  the  same  organism. 
But  we  may  also  find  Volvox  balls  in  which 
only  ova  are  produced,  and  others  in  which 
only  sperms  are  produced.  The  former  seem 
to  be  more  vegetative  and  nutritive  than 
the  latter;  we  call  them  female  and  male 
organisms  respectively;  we  are  at  the  founda- 
tion of  the  differences  between  the  two  sexes. 
Again  we  would  state  our  thesis  that  all 
through  the  animal  series,  from  active  Infu- 
sorians  and  passive  Gregarines,  to  feverish 


90  EVOLUTION 

Birds  and  sluggish  Reptiles,  we  read  alter- 
natives or  antitheses  between  activity  and 
passivity,  between  liberal  expenditure  of 
energy  and  a  more  conservative  habit  of 
storing.  This  primarily  depends  on  the 
ratio  between  disruptive  (katabolic)  processes 
and  constructive  (anabolic)  processes,  and 
we  regard  the  sexes  as  expressions  of  the 
same  contrast  within  a  given  species.  And 
do  not  kindred  yet  contrasted  forms,  like 
goat  and  sheep,  wasp  and  bee,  butterfly  and 
moth,  seem  as  it  were  but  the  extreme  ex- 
pression of  the  same  individual  and  sex 
contrasts  carried  farther,  upon  the  plane  of 
species,  of  genus,  of  order,  or  of  class .^ 

According  to  this  view  the  deep  constitu- 
tional difference  between  the  male  and  the 
female  organism,  which  makes  of  the  one  a 
sperm-producer  and  of  the  other  an  egg-pro- 
ducer, is  due  to  an  initial  difference  in  the 
balance  of  chemical  changes.  The  female 
seems  to  be  relatively  the  more  construc- 
tive, whence  her  greater  capacity  for  organic 
sacrifices  in  maternity;  the  male  relatively 
the  more  disruptive,  whence  his  usually  more 
vivid  life,  his  explosive  energies  in  action. 
In  short,  the  sexes  express  a  fundamental 
difference  in  the  rhythm  of  metabolism. 

This  initial  difference  not  only  leads  to  the 
primary  functional  distinction  between  male 


GREAT  STEPS  IN  EVOLUTION      91 

and  female,  but  it  also  determines,  either 
from  the  start,  or  after  maleness  and  female- 
ness  have  been  partly  established,  what  par- 
ticular expression  will  be  given  to  a  whole 
series  of  secondary  characters,  —  both  struc- 
tural and  functional,  —  whether  a  masculine 
or  a  feminine  expression. 

The  Beginnings  of  Brains. — In  most 
sponges  and  coelenterates  (such  as  jelly-fish, 
sea-anemones  and  coral  polyps)  the  body 
has  radial  symmetry.  That  is  to  say,  it  is 
the  same  all  round,  it  has  no  right  nor  left,  it 
can  be  cut  into  symmetrical  halves  along 
many  different  vertical  planes.  This  kind  of 
symmetry  is  well  suited  for  sedentary  life, 
like  that  of  sea-anemones,  which  wait  for 
food  to  come  within  the  scope  of  their  sting- 
ing and  grasping  tentacles;  or  for  an  easy- 
going life,  like  that  of  jelly-fishes,  which  live 
in  the  very  uniform  environment  of  the  open 
sea  where  all  directions  mean  very  much  the 
same. 

For  conditions  of  more  active  and  strenu- 
ous life,  however,  where  it  is  important  to 
chase  the  food,  to  flee  from  enemies,  to  pur- 
sue mates,  and  so  on,  radial  symmetry  is 
unsuitable,  and  it  is  replaced  by  bilateral 
symmetry.  This  acquisition  of  head  end  and 
tail  end,  of  right  side  and  left  side,  was  doubt- 
less of  enormous  importance,  both  in  itself 


92  EVOLUTION 

and  in  its  consequences,  which  include  our 
knowing  our  right  hand  from  our  left. 

It  is  likely  that  certain  "  worms  "  were  the 
first  animals  definitely  to  abandon  the  more 
primitive  radial  symmetry,  to  begin  moving 
with  one  part  of  the  body  always  in  front,  to 
acquire  head  and  sides.  And  if  one  end  of 
the  body  constantly  experienced  the  first 
impressions  of  external  objects,  it  seems 
reasonable  to  suppose  that  sensitive  and  ner- 
vous cells  would  be  most  developed  in  that 
much-stimulated,  and  otherwise  over-edu- 
cated, head  region.  But  a  brain  always 
arises  from  the  sinking  in  of  ectodermic  cells 
from  the  surface  of  the  embryo,  and  its  be- 
ginning in  the  cerebral  ganglion  of  the  sim- 
plest "worms"  is  thus  in  part  explained. 
It  is  difficult  to  over-estimate  the  importance 
of  the  establishment  of  an  anterior  brain  — 
a  chief  motor  and  sensory  and  co-ordinating 
nerve-centre  —  and  the  consequent  evolution 
of  a  head. 

The  Beginnings  of  Behaviour.  —  Jen- 
nings has  shown  that  some  unicellular  ani- 
mals "  behave  "  in  a  very  definite  way.  They 
are  not  mere  automata  which  rush  about  as 
long  as  their  spring  keeps  unrolling,  and  they 
are  more  than  the  mere  slaves  of  stimulus. 
There  are  some,  it  is  true,  which  seem  to 
have  only  one  kind  of  reaction  to  every  kind 


GREAT  STEPS  IN  EVOLUTION      93 

of  stimulus,  only  one  answer  to  every  ques- 
tion, but  there  are  others  whose  behaviour 
is  at  a  higher  level,  illustrating  what  may  be 
called  "  the  method  of  trial  and  error."  They 
"try"  one  kind  of  reaction  after  another, 
until,  in  some  cases,  they  give  the  effective 
response. 

But  while  we  cannot  doubt  that  the  be- 
ginnings of  behaviour  are  to  be  found  in  the 
Protozoa,  new  possibilities  must  have  opened 
up  whenever  head-brains  were  established. 
For  this  centralizing  of  the  nervous  system 
must  have  meant  a  new  integration,  a  more 
unified  control,  of  the  whole  organism. 

We  cannot  attempt  to  summarize  the 
discernible  steps  in  the  evolution  of  beha- 
viour, but  we  wish  to  press  home  the  fact  that 
what  we  are  so  familiar  with  to-day  is  the 
long  result  of  time.  We  see  behaviour  rising, 
along  one  line,  to  its  wonderful  instinctive 
expressions.  We  see  it  rising  (whether  fur- 
ther or  along  another  line  is  still  under  dis- 
cussion) into  intelligent  expression  where 
there  is  perceptual  inference.  Finally,  in 
man,  with  his  conceptual  inferences,  intel- 
ligent behaviour  becomes  rational  conduct. 

Progress  along  many  Lines.  —  In  his 
interesting  "Evolution  of  Plants,"  Dr.  Scott 
refers  to  the  important  fact  that  at  a  time  so 
remote  as  the  Devonian  period,  when  there 


94  EVOLUTION 

were  no  backboned  animals  higher  than 
fishes,  a  very  high  level  of  organization  had 
been  reached  by  the  plants.  There  were  in 
those  days  ferns  and  horsetails,  club-mosses 
and  Pteridosperms,  and  many  other  plants  of 
high  degree;  what  has  happened  since  has 
been  specialization  rather  than  great  ad- 
vance. It  is  true  that  the  fern-like  Pteir- 
dosperms  gave  rise  to  the  world-wide  Meso- 
zoic  Cycadophytes,  and,  in  still  later  times, 
to  the  true  Flowering  Plants,  but  there  was 
no  great  new  organic  invention  like  that  of 
the  seed,  for  which  the  flower  is  but  the  pro- 
tean birth-robe.  Since  that,  progress  has 
been  in  the  intensive  colonization  of  the 
earth  and  in  detailed  adaptations,  vegeta- 
tive and  floral,  manifold  and  exquisite. 

In  thinking  of  this,  we  must  remember,  in 
the  first  place,  that  while  the  Devonian 
period  is  inconceivably  remote,  there  was  an 
equally  inconceivable  stretch  of  ages  before 
it,  during  which  there  must  have  been  many 
a  great  step  among  plants  as  well  as  among 
animals.  In  the  second  place,  the  fact  that 
plants  have  made  no  such  very  great  advance 
since  the  Devonian  period,  whereas  animals 
have  risen  by  stride  after  stride  to  higher  and 
higher  levels  of  organization,  is  congruent 
with  the  deep  contrast  between  plants  and 
animals  to  which  we  have  already  referred. 


GREAT  STEPS  IN  EVOLUTION      95 

It  is  not  merely  that  plants  in  their  struc- 
tural relations  remain  about  the  level  of 
Ccelentera  among  animals;  it  is  that  they 
are  on  an  entirely  different  line  of  evolution. 
Plants  and  animals  are  incommensurable  and 
antithetic. 

If  we  take  a  series  of  sedentary  animals, 
such  as  zoophytes  or  alcyonarian  corals,  we 
find,  as  in  plants,  a  wealth  of  variety  within 
narrow  range,  an  exhausting  of  the  possi- 
bilities of  ramification  and  colony-making,  a 
great  development  of  hard  supporting  parts, 
and  many  nice  adjustments  to  slight  environ- 
mental peculiarities.  They  and  the  plants 
have  a  similar  kind  of  beaut}^ — expressing  the 
dream-smiles  of  their  sleep-like  life. 

How  different  this  is  from  what  we  see 
among  the  free-living  animals  —  which  made 
one  important  step  after  another.  Keeping 
to  backboneless  animals  for  the  moment,  let 
us  notice  some  of  the  great  acquisitions — ■ 
bilateral  symmetry,  a  head-brain,  specialized 
sense-organs,  a  body-cavity,  a  segmented 
body,  muscular  feet,  a  renewable  external 
armour,  muscular  jointed  appendages,  and  so 
on.  Or  let  us  think  of  particular  cases  such 
as  the  extraordinary  development  of  the  res- 
piratory system  in  insects,  where  ramifj^ing 
tubes  carry  air  to  every  nook  and  cranny  of 
the  body,  so  that  the  blood  can  hardly  ever 


96  EVOLUTION 

become  impure,  and  a  climax  of  vital  activity 
is  attained.  The  story  of  the  evolution  of 
Invertebrates  is  a  succession  of  great  achieve- 
ments. Among  Vertebrates  they  were  even 
greater. 

The  Ascent  of  Vertebrates. — It  is  a 
profitable  exercise  to  draw  a  long  ascending 
slope,  with  perpendiculars  dropped  from 
various  points  to  the  base  line,  registering  the 
evolutionary  ascent  of  Vertebrate  animals. 
What  are  the  impressive  facts  .^  (1)  Life  has 
been  creeping  or  pressing  upwards  for  many 
millions  of  years.  (2)  Great  specializations 
occur  at  every  level,  but  there  is  also  beyond 
doubt  a  progressive  differentiation  and  in- 
tegration. (3)  This  is  particularly  true  of 
the  nervous  system,  and  is  of  course  a 
condition  and  expression  of  the  gradual  in- 
crease of  intelligent  behaviour.  Life  becomes 
richer  and  freer.  (4)  Increased  individuation 
makes  reproductive  economy  possible.  Pa- 
rental care  increases,  and  the  number  of  off- 
spring decreases.  There  is  an  emergence  of 
the  finer  feelings,  and  fondness  is  sublimed 
in  love.  (5)  There  has  been  an  interesting 
peopling  of  the  earth,  an  establishment  of 
faunas  distinctive  of  the  shore,  the  open  sea, 
the  deep  sea,  the  fresh  waters,  and  the  air. 
Amphibians  mark  the  important  transition 
from  water  to  dry  land;   the  ancient  Ptero- 


GREAT  STEPS  IN  EVOLUTION      97 

y 

'  dactyls  mark  the  mastery  of  the  air  in  which 
Birds  and  Bats  are  now  most  at  home.  But 
hardly  less  impressive  is  the  possessing  of 
every  nook  and  corner.  Many  a  species  has 
only  a  niche,  but  it  is  its  own.  (6)  Following 
from  the  masterful,  detailed  colonization  of 
the  heavens  and  the  earth  and  the  waters 
under  the  earth,  there  is  the  wealth  of  con- 
summate adaptation — of  a  creature  to  its 
surroundings,  to  its  food,  to  its  habits;  of  the 
unborn  young  to  the  mother  and  of  the 
mother  to  the  unborn  young;  of  the  sexes  to 
one  another;  and  of  the  internal  architecture 
of  the  body,  whether  in  the  fit  adjustment  of 
the  proportions  of  parts,  or  in  the  minute 
structure  of  a  bone.  Every  creature  is  a 
bundle  of  adaptations.  Indeed,  as  Weis- 
mann  says  of  the  whale,  "When  we  take 
away  the  adaptations,  what  have  we  left .?  " 
It  is  instructive  to  look  into  the  matter  in 
detail,  and  to  notice,  for  instance,  what  types 
made  particular  acquisitions.  Hag  fishes 
and  lampreys  (Cyclostomes)  were  the  first 
animals  with  skulls;  fishes  were  first  with 
jaws;  amphibians  gained  fingers  and  toes, 
true  lungs,  a  voice,  and  a  mobile  tongue; 
reptiles  first  show  the  important  antenatal 
robes  (or  foetal  membranes)  called  the  amnion 
and  the  allantois,  and  the  crocodile  was  the 
first  creature  with  a  four-chambered  heart; 


98  EVOLUTION 

birds  and  mammals  are  the  only  warm- 
blooded animals,  and  they  show  a  great 
heightening  of  brain-development;  in  all 
mammals  except  a  few  primitive  forms  there 
is  an  extremely  important  and  usually  pro- 
longed intimate  connection  between  the 
mother  and  the  unborn  young. 

The  Ascent  of  Man. — As  this  final 
achievement  of  Vertebrate  evolution  will  be 
discussed  by  Dr.  Arthur  Keith  in  a  special 
volume  of  this  Library,  we  need  not  do  more 
than  refer  to  a  few  points  of  general  evolu-, 
tionary  interest. 

The  real  distinctiveness  of  man  from  his^ 
nearest  allies  depends  on  his  power  of  build- 
ing up  general  ideas  and  of  controlling  his 
conduct  in  relation  to  ideals.  He  has  many 
structural  peculiarities,  it  is  true,  but  the 
differentiating  qualities  are  in  language, 
thought  and  conduct,  and  in  the  finer  brain 
associated  with  these. 

The  "Descent  of  Man"  is  the  expansion 
of  a  chapter  in  the  "Origin  of  Species."  In 
other  words,  the  evidences  of  man's  origin 
from  an  ancestral  type  common  to  him  and 
to  the  higher  apes,  are  the  same  as  those  used 
to  substantiate  the  general  doctrine  of  de- 
scent. As  Owen  allowed  long  ago,  there  is  an 
"all-pervading  similitude  of  structure"  be- 
tween man  and  the  anthropoid  apes;    the 


GREAT  STEPS  IN  EVOLUTION      99 

bodily  life  is  closely  similar;  the  human  body 
is  a  rich  collection  of  vestigial  structures; 
some  of  the  fossil  remains  are  nearer  the 
anthropoid  type;  man's  individual  develop- 
ment is  in  some  ways  like  a  recapitulation  of 
his  presumed  ancestral  history. 

There  is  a  fine  ring  in  the  closing  words  of 
*'The  Descent  of  Man":— 

"We  must,  however,  acknowledge,  as  it 
seems  to  me,  that  man,  with  all  his  noble 
qualities,  with  sympathy  which  feels  for  the 
most  debased,  with  benevolence  which  ex- 
tends not  only  to  other  men,  but  to  the 
humblest  living  creature,  with  his  God-like 
intellect  which  has  penetrated  into  the  move- 
ments and  constitution  of  the  solar  system — 
with  all  these  exalted  powers — man  still 
bears  in  his  bodily  frame  the  indelible  stamp 
of  his  lowly  origin." 

Man's  antiquity  is  to  be  measured  not  In 
centuries  but  in  millennia.  It  is  perhaps 
150,000  years  since  he  used  stone  weapons  in 
Europe  against  mammoth  and  rhinoceros, 
hyaena  and  lion,  and  these  weapons  were  not 
the  work  of  novices.  No  fossil  remains  of 
man  have  been  found  except  in  Post-Tertiary 
(Diluvial)  deposits,  but  there  are  several 
reasons  for  believing  that  his  origin  was  very 
much  earlier.  Thus,  for  instance,  it  is  cer- 
tain that  he  did  not  arise  from  any  of  the 


100  EVOLUTION 

known  anthropoid  apes  (gorilla,  chimpanzee, 
orang  and  gibbon) ,  but  from  a  stock  common 
to  them  and  to  him;  therefore  it  is  likely  that 
the  human  stock  had  diverged  before  the 
time  when  the  anthropoid  apes  are  known 
to  have  been  established  as  a  distinct  family, 
namely  in  the  Miocene. 

It  is  possible  that  man  arose  as  a  mutation, 
as  an  anthropoid  genius  in  short,  but  the 
factors  that  led  to  his  emergence  are  all 
unknown.  We  must  remember,  however, 
that  the  stock  of  Primates  to  which  he  is 
zoologically  affiliated  is  marked  by  great  in- 
telligence, and  that  we  find  illustrated 
amongst  them  some  very  significant  habits — 
of  walking  half  erect,  of  using  sticks  and 
stones,  of  building  shelters,  of  living  in  fami- 
lies, of  co-operating  in  bands,  and  of  talking 
a  good  deal.  The  anthropoid  apes  are  not 
social,  but  many  monkeys  are,  and  there 
can  be  little  doubt  that  man  was  from  the 
first  distinctively  social.  "Man  did  not 
make  society;   society  made  man." 

The  uncertainties  as  to  man's  pedigree 
and  antiquity  are  still  great,  and  it  is  unde- 
niably difficult  to  discover  the  factors  in 
his  emergence  and  ascent.  Therefore,  while 
holding  firmly  to  the  general  conclusion  to 
which  the  facts  all  point,  we  do  well  to  treat 
the  problem  with  all  reverence,  especially 


GREAT  STEPS  IN  EVOLUTION    101 

when  we  reflect  on  the  greatness  of  the  re- 
sult of  this  last  great  step  in  organic  evolu- 
tion. For  "What  a  piece  of  work  is  a  man! 
How  noble  in  reason !  how  infinite  in  faculty, 
in  form  and  moving  how  express  and  admir- 
able! in  action  how  like  an  angel!  in  appre- 
hension how  like  a  god!  " 

A  chapter  can  merely  hint  at  the  great 
steps  in  evolution,  and  we  must  leave  the 
reader  to  develop  the  subject.  For  this  is 
certain  that  we  cannot  appreciate  the  fact 
of  evolution,  or  form  a  sound  judgment  in 
regard  to  its  factors,  unless  we  think  of  the 
age-long  process  in  some  detail  and  recognize 
at  once  the  grandeur  and  the  difficulty  of 
each  of  its  greater  uplifts. 

Evolution  as  Retrogressive:  Deteri- 
oration AND  Parasitism. — Of  "Degenera- 
tion: a  chapter  in  Darwinism,"  Sir  Ray 
Lankester  many  years  ago  wrote  a  whole 
volume,  compact  yet  readable:  still,  even 
to-day,  the  old  optimism  of  political  progress 
too  largely  colours  the  public  mind;  so, 
despite  knowledge  and  care,  all  save  the  most 
pessimistic  of  us  tend  sometimes  to  speak, 
and  it  may  be  even  write,  as  if  evolution 
necessarily  implied  progress,  and  as  if  the 
surviving  fittest  were  also  the  best,  in  its 
ordinary  sense,  of  better  than  mere  good. 
Hence  the  need  of  frankly  facing  some  of 


102  EVOLUTION 

those  ugly  chapters  of  natural  history  which 
follow  the  decline  of  so  many  forms  of  life, 
even  high  and  beautiful  ones,  into  degenera- 
tions well-nigh  incredible,  into  parasitisms 
even  loathsome.  For  one  thing,  even  the 
most  thoroughgoing  creationist  and  Paleyan 
of  old  must  have  had  some  qualms  in  ascrib- 
ing the  intricacies  of  parasitism  to  special 
creation,  or  its  pains  and  enfeeblement,  so 
varied  and  so  widespread  among  all  the 
higher  animals,  to  beneficent  design;  thus 
the  evolutionary  parasitologist  has  had  it 
practically  all  his  own  way,  yet  has  also 
cured  us,  with  his  gruesome  lists  of  pestif- 
erous creatures  and  lurking  dangers,  of  that 
dream  of  this  as  the  best  of  all  possible  worlds 
to  which  a  too  facile  evolutionism  has  been 
wont  to  incline.  Species  of  all  manner  of 
groups,  he  shows  us,  may  fall  into  parasi- 
tism, the  simplest  bacteria  and  lower  fungi, 
the  more  active  and  long  supposed  innocent 
Protozoa  above  all — so  that  for  a  generation 
past  the  vast  field  of  pathology  has  seemed 
well-nigh  divided  between  bacteriologist  and 
parasitologist  proper.  It  is  among  the  Ver- 
tebrates, which  only  fall  into  parasitism  in 
the  rarest  cases,  that  infestation  is  most 
frequent.  Fishes  may  even  swarm  exter- 
nally with  trematodes  and  parasitic  crus- 
taceans, internally  with  cysts  and  intestinal 


GREAT  STEPS  IN  EVOLUTION    103 

worms  without  number.  A  vivid  impres- 
sion of  the  prevalence  of  parasitism  is  afforded 
by  the  capture,  not  infrequent  at  a  chan- 
nel zoological  station  or  by  fisher  folk  any- 
where, of  the  huge  and  majestic  sunfish, 
Orthagoriscus  mola;  and  by  picking  off  with 
forceps  into  museum  bottles  his  crowds  of 
uninvited  passengers — the  tuft  of  barnacles 
upon  his  back,  the  biting  isopods  like  enor- 
mous fleas  upon  his  skin,  the  trematodes 
sucking  like  leeches  upon  his  eyes;  and  within 
to  find  not  only  his  alimentary  canal 
crammed  with  worms  more  than  with  food, 
and  his  liver  changed  from  its  natural  brown 
almost  into  the  likeness  of  a  tangle  of  white 
worsted,  of  which  each  thread} is  a  tape- 
worm. Neither  frog  nor  lizard,  serpent  nor 
bird,  escapes;  indeed  birds  are  peculiar  suf- 
ferers, witness  the  too  common  "gapes"  of 
poultry,  a  choking  of  the  windpipe  by  thread- 
worms, and  the  numerous  parasitic  worms 
which  Mr.  Shipley's  labours  have  discovered 
in  the  well-nigh  sacred  grouse.  Of  ticks  the 
shepherd  is  only  beginning  to  know  the  full 
dangers,  as  of  fleas  man  himself.  Apart 
from  bacterial  and  protozoan  pests,  as  yet 
beyond  counting,  man  is  debited  by  the 
parasitologist  with  at  least  sixty  species; 
some  reckon  twice  as  many.  The  amazingly 
varied  methods  of  Nature  for  the  diffusion 


104  EVOLUTION 

of  parasites  are  among  the  very  strangest 
disentanglements  of  the  web  of  life,  but  into 
the  stories  of  these  adventures  in  search  of 
mischief  we  cannot  enter  here:  enough  if  we 
note  the  stupendous  rate  of  multiplication 
by  which  the  many  chances  against  finding 
the  proper  host  are  constantly  met;  thus 
the  common  tape-worm  of  man  has  been 
calculated  to  produce  eighty-five  million  ova 
during  its  two  years'  existence. 

It  is  an  interesting  inquiry  whether  the 
large  numbers  of  so-called  species  of  thread- 
worms, tape-worms  and  other  parasites,  are 
not,  in  many  cases  at  least,  mere  modifica- 
tion forms,  whose  diagnostic  characters  are 
directly  induced  by  the  peculiarities  of 
their  respective  hosts.  The  question  is,  of 
course,  one  for  the  experimental  observer. 

Again,  even  parasitism  must  not  be  viewed 
too  pessimistically.  It  is,  after  all,  not  the 
interest  of  the  parasite  to  kill  its  host,  or 
even  to  deteriorate  its  life  too  seriously; 
moreover  the  host  becomes  more  or  less 
adapted  to  its  wonted  guests,  and  probably 
correspondingly  immune  to  the  irritant 
poisons  which  many  parasites  have  been 
shown  to  excrete.  The  rapid  disaster  which 
parasites  so  often  bring  about  seems  rather 
when  introduced  into  some  new  and  unac- 
customed host;  as  probably  in  the  case  of 
sleeping  sickness. 


GREAT  STEPS  IN  EVOLUTION    10 


/r 


Again,  parasitism  may  pass  on  one  side 
towards  more  and  more  complete  mutual 
adaptation,  witness  the  symbiosis  of  alga 
and  animal  in  certain  sea-anemones,  or 
the  admirable  permanence  of  that  co-opera- 
tion of  short-lived  alga  and  transient  mould 
which  enables  the  resultant  lichen  sometimes 
to  outlive  the  very  tree  which  bears  it. 
Galls,  again,  afford  many  instances  of  a 
parasitism  which  is  reaching  equilibration. 

Thus  in  many  ways  we  must  not  consider 
parasites  as  simply  aberrant,  nor  their  peculi- 
arities as  unique.  These  become  intelligible 
products  of  evolution  when  we  realize  them 
as  perhaps  the  extreme  cases  of  the  deter- 
mination of  organism  by  environment.  From 
the  analysis  of  this  relation,  especially  in 
these  extreme  cases  of  parasite  and  host,  the 
theory  of  evolution  might  almost  have  been 
predicted,  since,  if  the  details  of  environ- 
ment and  of  organism  be,  as  here,  obviously 
and  precisely  adapted  one  to  the  other, 
change  in  the  former  must  either  be  followed 
by  the  extinction  of  the  latter,  or  by  its 
modification  in  the  requisite  details.  To 
understand  the  modus  operandi  of  this, 
Weismann  invokes  the  needful  germinal 
variation  of  the  germ-cells,  and  Dohrn  his 
"principle  of  functional  change"  —  his  re- 
minder   that   every    living   tissue,    however 


106  EVOLUTION 

specialized,  retains  traces  of  all  the  func- 
tions of  protoplasm,  and  that  therefore  any- 
one of  these  may  be  indefinitely  increased 
by  favourable  conditions,  and  the  specialized 
function  similarly  reduced  to  a  trace.  Our 
notion  of  specialization  becomes  thus  asso- 
ciated with  a  corresponding  possibility  of 
simplification,  and  our  idea  of  progress  thus 
becomes  complemented  and  checked  by  the 
possibility  of  degeneration,  and  this  from 
any  stage  of  the  ascent  of  life.  The  first 
of  these  views  is  the  neo-Darwinian;  while 
the  second  savours  of  neo-Lamarckianism; 
but  here,  happily,  is  a  case  in  which  the 
recent  admirable  eirenicon  of  Lloyd  Morgan, 
Osborn  and  Baldwin  (discussed  in  Chapter 
VI)  may  be  conveniently  applied.  Accord- 
ing to  this,  the  modifications  of  the  indi- 
vidual in  response  to  environment,  to  use 
and  disuse,  in  themselves  non-heritable 
though  they  may  be,  may  yet  serve  as  the 
nurse  and  shield  and  selective  vantage- 
ground  for  germ-variations  in  the  same 
direction.  With  this  two-fold  process  at 
work,  in  germs  and  in  developing  adults, 
the  frequent  development  of  parasitic  shoots 
upon  the  tree  of  life  becomes  a  less  per- 
plexing marvel. 

Another  interest  of  this  subject  is  the  way 
in  which  it  invites  that  comparison  of  the 


GREAT  STEPS  IN  EVOLUTION    107 

natural  and  the  social  world  which  has 
always  been  so  fascinating,  and,  as  we  main- 
tain from  opening  to  close  of  this  volume, 
also  so  fruitful.  The  naturalist  and  phy- 
sician almost  forget  that  the  word  parasite 
was  originally  a  social  epithet;  but  the 
many  critics  of  human  society  are  using 
the  comparison  more  and  more  frequently, 
of  course  often  in  mere  vague  abuse,  but 
sometimes  keenly  also.  Notable  in  this 
connection  is  the  collaboration  of  Professor 
Massart,  a  biologist  of  Brussels,  with  M. 
Emile  Vandervelde,  now  widely  known  be- 
yond the  Belgian  parliament  as  one  of  the 
foremost  of  the  popular  tribunes  of  Europe; 
and  their  "Parasitism,  Organic  and  Social" 
(1895)  will  still  be  found  suggestive  to  natur- 
alist and  sociologist  alike. 

Without  entering  upon  matters  so  con- 
troversial as  a  volume  so  named  inevitably 
raises,  we  may  profitably  note  the  fresh 
light  which  the  study  of  parasitism  throws 
upon  that  till  lately  accepted  and  still 
mainly  predominant  body  of  economical 
and  social  thought,  that  of  the  modern 
industrial  age — its  political  economy  for  the 
group,  its  teaching  and  ideal  of  success  for 
the  individual.  For  thus  instead  of  calling 
this  one  or  that  of  our  more  successful  fel- 
lows by  the  ugly  name  of  parasite,  we  may 


108  EVOLUTION 

more  safely  begin  by  recognizing  this  very 
tendency  in  ourselves.  For  who  does  not 
at  times  look  forward  to  a  more  peaceful, 
a  more  prosperous  and  assured  period,  in 
which,  storms  and  trials  over,  we  are  to 
settle  down,  snug,  cosy  and  warm,  there  to 
eat  of  the  fat,  and  drink  of  the  sweet,  and 
to  enjoy  what  may  remain  to  us  of  life? 
And  what  parent  but  wishes  for  his  child  a 
safer,  easier,  richer  life  than  his  own?  Little 
wonder,  then,  that  the  political  economist, 
who  has  for  the  most  part  but  massed  popu- 
lar opinion  into  his  pretentious  but  inchoate 
would-be  science,  has  treated  this  scheme 
of  life  as  the  natural  one,  and  confirmed  his 
public  more  and  more  into  it  as  the  practical 
one  as  well.  For .  your  would-be  practical 
man,  slave  to  that  wildest,  strangest,  most 
impossible  of  all  theories — the  theory  that 
there  are  no  theories — ever  falls  victim  to 
the  surface  plausibility  of  the  crudest  theory 
going. 

Whereas  the  student  who  has  seen  crusta- 
cean larvae  in  all  the  activity  of  their  youth, 
bright-eyed,  free-swimming,  and  thereafter 
settling  down  into  barnacles  upon  the  rock, 
or,  seeking  food  and  safety  at  the  expense 
of  their  larger  and  stronger  active  kindred, 
settling  further  down  into  mere  blood-bags, 
mere  egg-bags,  "sans  eyes,  sans  ears,  sans 


GREAT  STEPS  IN  EVOLUTION    109 

everything,'*  has  before  him  a  nature- 
symbol,  one  worth  thinking  about,  and 
that  carefully,  even  furiously  also.  For  here 
it  turns  out  that  the  teaching  of  the  econo- 
mists who  have  identified  comfort  with 
progress  have  been  so  far  right  in  unifying 
them,  no  doubt;  only  they  have  been  for- 
getting that  such  progress  tends  to  be 
bought  too  dearly.  Their  gospel  of  "getting 
on"  is  not  necessarily  getting  on;  and 
hence  their  much  preached  and  yet  more 
prayed  for  "success  in  life"  so  often  turns 
out  the  very  reverse  of  success  in  living. 

Contrariwise,  our  bio-sociology  tends  to 
justify  the  so-called  "unpractical."  It  is 
essentially  the  free-living  and  self-supporting 
creatures  that  really  get  on,  that  evolve  in 
the  best  sense.  So  the  idealist  adventurer 
who  loves  to  meet  the  "bright  eyes  of 
danger,"  who  goes  out  to  seek  love  and  face 
death,  has  true  success  in  life,  brief  though 
it  be;  and  this  not  merely  from  the  "ro- 
mantic" point  of  view  the  philistines  fancy 
confined  to  novels,  but  from  that  rising 
standpoint  of  evolutionist  realism  of  which 
morals  in  one  age,  religion  in  another,  and 
now  art  in  our  own,  have  each  been  the 
presage.  Thus  in  facing  the  ugliest  facts  of 
lowest  life  we  see  them  give  way  to  the 
noblest   hopes   of   our   own   evolution.      In 


no  EVOLUTION 

1 

education,  then,  let  us  not  fear  to  apply  this 
escape  from  economics  of  the  baser  sort, 
that  science  falseliest  so  called;  and  thus 
have  done  with  the  current  obsessions  of  the 
money-world,  of  most  ease  with  least  labour, 
of  getting  something  for  nothing;  perhaps 
above  all,  of  that  seeking  after  the  assured 
life  of  petty,  sedentary  functionarism,  which 
is  becoming  a  main  curse  of  civilization — ■ 
we  now  see  why. 

Out  in  the  fields,  on  hill,  at  sea,  facing  the 
buffetings  of  wind  and  wave,  working  with 
our  fellows,  and  there  content  neither  with 
strength  nor  skill  alone,  but  seeking  exercise 
for  both,  here  is  the  best  life  of  evolving 
manhood :  as  of  old,  so  for  ever,  let  townlings 
dream  as  they  may.  And  how  to  combine 
this  fundamental  vividness  of  rustic  life 
with  the  subtler,  yet  it  may  be  even  more 
strenuous  life  of  productive  urban  culture, 
is,  perhaps,  the  main  problem  before  the 
evolutionist.  In  modern  everyday  phrase 
this  task  is,  in  fact,  already  opening  before 
us;  already  we  are  seeking  to  advance  rural 
development  here  and  town-planning  there; 
we  have  next  to  co-ordinate  both  into 
regional  renewal.  Given  this  incipient  view 
and  policy  of  human  life,  as  consciously 
evolutionary,  in  exchange  for  the  passing 
one — of    successful    life    as    sessile,    uncon- 


GREAT  STEPS  IN  EVOLUTION    111 

sciously  degenerative,  and  as  far  as  possible, 
parasitic — the  field  of  effort  opens.  Hygiene, 
engineering  and  irrigation,  agriculture  and 
forestry,  and  all  such  strenuous  careers  are 
already  opening  perspectives  lately  un- 
dreamed by  youth,  struggles  for  existence 
nobler  and  more  sustainedly  strenuous  than 
those  of  war.  Practically,  the  control  of  the 
ice-lands  and  of  the  tropics,  the  amend- 
ment of  nature — and  above  all,  specula- 
tively, the  distinction  between  ascending 
and  deteriorative  progress — thus  alike  be- 
come more  clear. 


CHAPTER  IV 

VARIATION     AND      HEREDITY:      THE      SPRINGS 
AND    CHANNELS   OF   EVOLUTION 

What  Organic  Evolution  Implies — Heredity  and  Variation 
— Why  Like  Tends  to  Beget  Like — Organic  Changes 
Analyzed — Darwin's  Position  in  regard  to  Variations — 
Modern  Study  of  Variations — The  Mutation  Theory 
— MendeUsm — Causes  of  Variation. 

What  Organic  Evolution  Implies. — Or- 
ganic evolution  is  racial  change  along  a 
definite  line.  It  is  for  the  variety  or  species, 
breed  or  race,  what  embryonic  development 
is  for  the  individual — a  mode  of  becoming. 
Its  continuity  is  sustained  by  a  succession  of 
generations,  whereas  in  development  the  con- 
tinuity is  obviously  one  of  personal  identity. 
Evolution  implies  three  things:  (a)  raw  ma- 
terials in  the  form  of  variations,  or  organic 
changes  of  some  sort;  (6)  an  arrangement  for 
securing  the  hereditary  entail  of  some  of 
these;  and  (c)  a  directive  mechanism  for 
securing  consistency  and  effectiveness  of 
racial  change.  The  importance  of  (c)  will 
vary  with  what  is  provided  by  (a)  and  with 
the  degree  of  persistence  allowed  by  (b). 
Heredity  and  Variation.  —  Heredity  is 

112 


VARIATION  AND  HEREDITY      113 

the  genetic  relation  between  successive  gen- 
erations, and  an  inheritance  includes  all  that 
an  organism  is,  or  has,  to  start  with,  in 
virtue  of  its  hereditary  relation.  We  cannot 
compare  organic  inheritance  to  a  patrimony; 
for  the  organism  and  its  inheritance  are,  to 
begin  with,  one  and  the  same.  Nor  do  we 
any  longer  think  of  heredity  as  a  power  or  a 
principle,  as  a  fate  or  a  force;  we  study  it 
as  a  genetic  relation,  which  is  sustained  by 
a  visible  material  basis,  namely  the  germ- 
cells;  as  a  relation  of  resemblances  and 
differences  which  can  be  measured  and 
weighed,  or  in  some  way  computed. 

The  hereditary  relation  is  such  that  like 
tends  to  beget  like,  while  at  the  same  time 
opportunity  is  afforded  for  the  individual 
new  departures  which  we  call  variations. 
Both  the  tendency  to  persist  and  the  ten- 
dency to  diverge  are  included  in  the  heredi- 
tary relation,  so  that  it  is  confusing  to  make 
an  absolute  antithesis  between  heredity  and 
variation.  Heredity,  seen  in  its  fullest 
sense,  is  the  larger  concept,  and  includes 
both  inertia  and  divergence,  both  con- 
tinuance and  change.  Whatever  be  the 
terms  used,  there  are  two  complemental 
facts:  that  like  tends  to  beget  like,  yet  that 
every  new  creature  has  in  some  way  an 
individuality  of  its  own. 


114  EVOLUTION 

Why  Like  Tends  to  Beget  Like.  —  The 
fundamental  hereditary  relation  is  such  that 
like  tends  to  beget  like,  and  the  reason  for 
this  is  found  in  the  fact  of  germinal  con- 
tinuity.   As  long  ago  as  1875,  Galton  pointed 
out  that  there  is  a  sense  in  which  the  child 
is  as  old  as  the  parent;  for  when  the  parent's 
body  is  developing  from  the  fertilized  ovum, 
a  residue  of  unaltered  germinal  material  is 
kept  apart  to  form  the  reproductive  cells, 
one    of    which    may    become    the    starting- 
point  of  a  child.     This  idea  has  been  in- 
dependently expressed  and  more  fully  de- 
veloped by  Weismann,  who  states  it  thus: 
"In  development  a  part  of  the  germ-plasm 
[i.e.   the    essential    germinal    material]    con- 
tained in  the  parent  egg-cell  is  not  used  up 
in  the  construction  of  the  body  of  the  off- 
spring, but  is  reserved  unchanged  for  the 
formation  of  the  germ-cells  of  the  following 
generation."     In  many  cases  the  future  re- 
productive cells  are  visibly  set  apart  at  a 
very  early  stage  before  the  division  of  labour 
in  body-making  has  more  than  begun;    in 
other  cases  where  the  future  reproductive 
cells  are  not  visible  till  much  later,  we  argue 
by  analogy  that  they  are  reproductive  cells 
because    they    have    not    shared    in    body- 
making,    but  have   kept   intact   the   proto- 
plasmic  equipment — the   full   inheritance — 


VARIATION  AND  HEREDITY      115 

of  the  original  fertilized  ovum.  Thus  the 
parent  is  rather  the  trustee  of  the  germ- 
plasm  than  the  producer  of  the  child.  In 
a  new  sense  the  child  is  "a  chip  of  the  old 
block."  The  clarifying  and  corroboration  of 
this  doctrine  of  germinal  continuity  has 
been  one  of  the  most  important  steps  of 
post-Darwinian  biology.  It  enables  us  to 
understand  why  like  tends  to  beget  like; 
and  it  also  suggests,  what  is  hardly  less  im- 
portant, that  the  new  departures  or  varia- 
tions, which  we  have  spoken  of  as  individual, 
are  really  expressions  of  the  changeful  vitality 
of  the  undying  germ-plasm.  As  Bergson 
puts  it:  "Life  is  like  a  current  passing  from 
germ  to  germ  through  the  medium  of  a 
developed  organism.  .  .  .  The  essential  thing 
is  the  continuous  progress  indefinitely  pur- 
sued, an  invisible  progress,  on  which  each 
visible  organism  rides  during  the  short 
interval  of  time  given  it  to  live." 

Organic  Changes  Analyzed. — Great 
progress  has  been  made  in  recent  years  in 
studying  the  individual  peculiarities  of  plants 
and  animals,  in  registering  their  amount 
and  their  frequency.  The  collection  and 
analysis  of  these  "biometric"  data  are  of 
fundamental  importance,  for  the  Darwinian 
method  of  interpretation  is  like  that  of 
Lyell,  throwing  the  light  of  the  present  on 


116  EVOLUTION 

the  darkness  of  the  past;  and  it  is  only 
when  we  know  securely  what  changes  are 
going  on  now  that  we  can  legitimately  argue 
back  to  what  may  have  occurred  in  remote 
antiquity. 

Facts  bearing  upon  variations  have  been 
gathered  so  industriously  of  late  that  as- 
similation has  hardly  kept  pace  with  accumu- 
lation; and  one  evidence  of  this  is  to  be  found 
in  the  confusing  ambiguity  of  the  terms  used 
by  various  biologists.  The  term  "varia- 
tion" is  used  in  reference  to  at  least  three 
readily  distinguishable  kinds  of  organic 
change,  and  the  term  mutation  is  also  used 
in  three  senses.  The  terminology  will  require 
to  be  standardized  by  some  International 
Congress  of  Biologists;  but  pending  this, 
let  us  do  what  we  can  in  trying  to  get  the 
ideas  clear. 

When  we  compare  a  number  of  members  of 
the  same  species — men,  ruffs,  garter-snakes, 
sticklebacks,  snails,  brambles,  buttercups, 
pansies,  and  so  on  —  we  find  that  they  differ 
from  one  another.  These  differences  can  be 
measured  and  registered  under  the  title 
"observed  differences,"  which  commits  us 
to  no  theory  whatever. 

But  these  "observed  differences"  require 
further  analysis  before  a  statement  of  them 
can  be  very  useful.     Indeed  a  statement  of 


VARIATION  AND  HEREDITY      117 

them  without  analysis  is  very  apt  to  lead  to 
biological  fallacy.  Many  of  the  differences 
may  be  wrapped  up  with  sex,  and  these  can 
be  readily  sifted  out  from  the  slumped  total. 
Others  may  be  wrapped  up  with  age,  and 
these  can  also  be  analyzed  out.  Others  are 
due  to  something  unusual  in  the  "nurture" 
in  the  wide  sense;  that  is,  they  are  the  direct 
results  of  peculiarities  in  surrounding  influ- 
ences and  of  peculiarities  of  habit.  Such 
changes  in  the  bodies  of  plants  and  animals 
are  extrinsic,  not  intrinsic,  in  origin;  they  are 
acquired,  not  inborn.  They  are  technically 
called  "acquired  characters,"  or  much  more 
clearly  "modifications."  They  may  be  de- 
fined as  structural  changes  in  a  part  of  the 
body,  directly  induced  by  peculiarities  of  use 
or  disuse,  or  by  some  change  in  surroundings 
and  nurture  generally,  which  transcend  the 
limit  of  organic  elasticity  and  thus  persist 
after  the  inducing  conditions  have  ceased  to 
operate.  No  convincing  evidence  of  their 
transmission  has  as  yet  been  forthcoming. 

Now  the  point  is  that  when  we  subtract 
from  the  total  of  observed  differences  all 
that  can  be  regarded  as  individual  modi- 
fications, we  have  a  very  interesting  remain- 
der, which  we  thus  define  off  as  inborn  or 
germinal  variations.  They  are  intrinsic,  not 
extrinsic;    inborn,    not   made.      We   cannot 


118  EVOLUTION 

causally  relate  them  in  a  direct  way  to  pe- 
culiarities in  habits  or  surroundings;  they 
are  often  distinct  at  birth  or  even  hinted  at 
before  birth;  they  are  rarely  alike  even  among 
forms  whose  conditions  of  life  are  uniform. 
They  are  in  many  cases,  if  not  always,  trans- 
missible. They  form  the  raw  material  of 
evolution. 

Darwin's  Position  in  regard  to  Varia- 
tions.— Darwin  recognized  two  kinds  of 
hereditary  variations,  in  addition  to  those 
extrinsic  changes  which  we  now  call  modi- 
fications. In  the  first  place  he  recognized 
large  "single  variations"  or  "sports,"  which 
occur  rarely  and  result  in  conspicuous  diver- 
gences from  the  type  of  the  species.  In  the 
second  place  he  recognized  slight  "individ- 
ual variations,"  which  are  practically  ubi- 
quitous, distinguishing  child  from  parent, 
brother  from  brother,  cousin  from  cousin. 
Both  of  these  kinds  of  variations  were  called 
"indefinite"  and  "spontaneous,"  to  dis- 
tinguish them  from  what  he  somewhat 
unfortunately  called  "definite  variations" 
— the  direct  result  of  environmental  and 
functional  peculiarities.  These  correspond  to 
what  we  now  call  modifications,  and  it  must 
be  noted  that  Darwin  believed  in  their  oc- 
casional transmissibility. 

Leaving  aside  the  question  of  the  possible 


VARIATION  AND  HEREDITY      119 

racial  importance  of  modifications,  it  is  of 
interest  to  notice  Darwin's  view  of  the 
relative  importance  of  *' single  variations" 
and  "individual  variations."  The  former 
correspond  in  a  general  way  to  what  we 
now  call  "discontinuous  variations,"  "muta- 
tions," "saltatory  variations";  the  latter  to 
"continuous  variations"  or  "fluctuations." 
Darwin  was  much  interested  in  the  former 
class,  "sports"  as  he  sometimes  called  them; 
but — true  to  the  influence  of  Lyell — he  came 
deliberately  to  the  conclusion  that  the  minute 
ubiquitous  fluctuations  were  by  far  the  more 
important.  The  criticism  of  Fleeming  Jen- 
kin,  Professor  of  Engineering  in  Edinburgh, 
that  single  large  peculiarities  would  be  likely 
to  be  swamped  by  inter-crossing,  had  so 
much  weight  with  Darwin  that  he  ceased  to 
attach  importance  to  the  larger  divergences, 
and  found  his  raw  material  in  the  smaller 
fluctuations.  "The  more  I  work,"  he  said, 
"the  more  I  feel  convinced  it  is  by  the  ac- 
cumulation of  such  extremely  slight  varia- 
tions that  new  species  arise."  We  shall 
return  to  this  question,  but  we  may  note  in 
passing  (1)  that  there  is  no  reason  to  believe 
that  "single  variations"  necessarily  occur 
singly,  the  fact  being  that  numerous  sports 
in  the  same  direction  sometimes  occur  simul- 
taneously; (2)  that  some  of  the  discontinuous 


120  EVOLUTION 

variations  that  have  been  studied  have  proved 
themselves  to  have  remarkable  staying  power 
in  inheritance,  being  anything  but  liable  to 
swamping;  and  (3)  that  we  have  not,  even 
to  this  day,  sufficient  knowledge  of  what 
Darwin  never  seems  to  have  doubted,  namely 
the  degree  of  heritability  of  the  minute  fluc- 
tuations. It  was  probably  a  false  step  on 
Darwin's  part  when  he  turned  so  fully  away 
from  discontinuous  variations. 

Modern  Study  of  Variations. — One  of 
the  great  steps  of  progress  in  evolution  lore 
since  Darwin's  day  has  been  what  we  see,  for 
instance,  in  Dr.  J.  A.  Allen's  pioneer  measure- 
ments of  American  birds  (1871),  in  Bateson's 
*' Materials  for  the  Study  of  Variation" 
(1894),  and  in  the  pages  of  the  journal  called 
"Biometrika" — the  recording  and  registra- 
tion of  the  variations  that  do  actually  occur 
in  nature.     A  few  results  may  be  noted. 

It  has  been  clearly  shown  that  Darwin  did 
not  in  the  least  exaggerate  the  available 
supply  of  raw  material.  "Even  Darwin 
himself,"  as  Wallace  says,  "did  not  realize 
how  much  and  how  universally  w^ild  species 
vary. "  It  has  been  proved  that  great  varia- 
tion is  as  frequent  in  wild  as  in  domesticated 
animals.  The  fountain  of  change  is  even 
more  copious  than  was  dreamed  of. 
-  Another    important   fact    has    come   out 


VARIATION  AND  HEREDITY      121 

clearly,  especially  from  the  pioneering  work 
of  Gallon,  that  there  is  often  a  proportion 
between  the  frequency  of  a  particular  varia- 
tion and  the  amount  of  its  deviation  from 
the  mean  of  the  character  in  question.  Let 
us  take  Wallace's  illustration,  which  makes 
this  point  clear  at  a  glance :  Among  measure- 
ments of  2,600  men,  taken  at  random,  there 
is  1  of  4  ft.  8  in.  and  1  of  6  ft.  8  in.;  12  of  5  ft. 
and  about  12  of  6  ft.  4  in.;  i.e.  equal  num- 
bers at  equal  distances  from  the  mean  of  5  ft. 
8  in.  In  other  words,  when  the  frequency 
and  the  magnitude  of  the  variations  are 
registered,  they  often  show  what  is  called  the 
Normal  Curve  of  Frequency. 

This  tedious  task  of  registering  the  varia- 
tions that  occur  may  seem  far  from  life-lore, 
but  a  little  consideration  and  a  little  actual 
registration — of  buttercup  petals,  of  length 
of  bird  wings,  of  brittle-star  arms,  of  jelly-fish 
canals,  or  the  like — will  convince  the  student 
that  biometrics  may  lead  him  into  the  very 
heart  of  the  matter.  If  the  registration  of 
the  dimensions  of  a  particular  character  be 
carried  on  year  after  year  in  similar  material, 
and  show  a  consistent  increase  in  the  asym- 
metry or  skewness  of  the  curve,  this  must 
mean  that  the  species  is  moving  in  a  definite 
direction  as  regards  the  particular  character 
measured.     Similarly,  the  persistent  occur- 


122  EVOLUTION 

rence  of  a  well-substantiated  double-humped 
curve — not  the  result  of  modificational 
effects — may  vividly  bring  home  the  fact 
that  the  species  is  dividing  into  two  sub- 
species. Thus,  by  a  statistical  path,  we  are 
brought  face  to  face  with  the  most  vital  of 
all  facts  —  revolution  creatrice. 

The  rapidly  growing  body  of  facts  in  re- 
gard to  variation  is  also  confirming  what 
Darwin  called  the  "correlation  of  varia- 
tions." He  pointed  out  that  the  whole 
organization  is  so  tied  together  during  its 
growth  and  development  that,  when  slight 
variations  in  any  part  occur,  and  are  trans- 
mitted, and  are  accumulated  by  natural 
selection,  other  parts  of  the  structure  may 
also  undergo  change,  apparently  irrespective 
of  any  advantage.  The  whole  framework  is 
so  knit  together  that  if  one  member  suffer 
change  others  suffer  with  it. 

The  idea  of  correlation  suggests  that  the 
organism  often  changes  as  a  unity  in  many 
parts  at  once,  and  not  like  a  machine  that  is 
perfected  piecemeal  by  the  accumulation  of 
many  little  patents  independent  of  each  other. 
Thus  a  variation  important  in  the  present 
may  bring  in  its  train  one  that  is  destined  to 
be  important  in  the  future,  and  a  variation 
too  small  in  itself  to  be  of  value  may  be 
carried  over  the  dead  point  into  effective- 


VARIATION  AND  HEREDITY      123 

ness  because  it  is  correlated  with  another 
variation  of  greater  momentum  or  vital  value. 

Another  result  of  modern  studies  on  varia- 
tion requires  to  be  stated  very  cautiously. 
Evidence  is  accumulating  to  show  that 
organic  structure  may  pass  with  seeming 
abruptness  from  one  position  of  equilibrium 
to  another.  Changes  of  considerable  amount 
sometimes  occur  at  a  single  leap.  These 
brusque  changes  are  called  *' discontinuous 
variations,"  or  sometimes  "sports,"  and,  in 
certain  cases,  "mutations."  There  is  nothing 
new  in  the  suggestion  that  evolution  may 
sometimes  have  been  by  leaps  and  bounds, 
for  this  was  a  favourite  idea  of  Cuvier's 
evolutionist  contemporary  and  antagonist, 
Etienne  Geoff roy  Saint-Hilaire;  and  it  was 
also  a  pet  heresy  of  Huxley's.  There  is 
nothing  new  in  recognizing  that  discontinu- 
ous variations  do  occur,  for  they  correspond 
to  Darwin's  "single  variations"  or  "sports." 
What  is  new  is  that  we  are  beginning  to 
accumulate  facts  in  regard  to  their  fre- 
quency and  their  heritability. 

Sir  Francis  Galton  compared  organic 
structure  to  a  polygonal  model,  so  shaped  as 
to  stand  on  any  one  of  its  sides.  "The  model 
and  the  organic  structure  have  the  cardinal 
fact  in  common,  that  if  either  is  disturbed 
without  transgressing  the  range  of  its  sta- 


124  EVOLUTION 

bility,  it  will  tend  to  re-establish  itself,  but 
if  the  range  is  overpassed,  it  will  topple  over 
into  a  new  position;  also  that  both  of  them 
are  more  likely  to  topple  over  towards  the 
position  of  primary  stability  than  away 
from  it." 

The  Mutation  Theory. — In  1900  Pro- 
fessor Hugo  de  Vries  of  Amsterdam  published 
under  the  title  "The  Mutation  Theory"  an 
account  of  his  very  interesting  and  important 
experiments  and  observations  on  the  origin 
of  species  in  the  vegetable  kingdom.  The 
most  striking  of  his  conclusions  was  that 
species  arise  from  one  another  by  discontinu- 
ous leaps  and  bounds,  as  opposed  to  a  con- 
tinuous process.  Whereas  Darwin  relied  on 
the  action  of  selection  on  minute  individual 
variations  or  fluctuations,  De  Vries  believes 
that  these  have  nothing  to  do  with  the  origin 
of  species,  which  appear  "all  at  once"  by 
mutations.  Let  us  quote  some  of  his  char- 
acteristic statements. 

"By  the  mutation  theory  I  mean  the 
proposition  that  the  attributes  of  organisms 
consist  of  distinct,  separate  and  independent 
units.  These  units  can  be  associated  in 
groups,  and  we  find,  in  allied  species,  the  same 
units  and  groups  of  units.  Transitions,  such 
as  we  so  frequently  meet  with  in  the  external 
form  both  of  animals  and  plants,  are  as  com- 


VARIATION  AND  HEREDITY      125 

pletely  absent  between  these  units  as  they 
are  between  the  molecules  of  the  chemist." 

"The  adoption  of  this  principle  influences 
our  attitude  towards  the  theory  of  descent 
by  suggesting  to  us  that  species  have  arisen 
from  one  another  by  a  discontinuous,  as 
opposed  to  a  continuous,  process.  Each  new 
unit,  forming  a  fresh  step  in  this  process, 
sharply  and  completely  separates  the  new 
form  as  an  independent  species  from  that 
from  which  it  sprang.  The  new  species  ap- 
pears all  at  once;  it  originates  from  the 
parent  species  without  any  visible  prepara- 
tion, and  without  any  obvious  series  of 
transitional  forms." 

"The  mutation  theory  is  opposed  to  that 
conception  of  the  theory  of  selection  which  is 
now  prevalent.  According  to  the  latter  view 
the  material  for  the  origin  of  new  species  is 
afforded  by  ordinary  or  so-called  individual 
variation.  According  to  the  mutation  theory 
individual  variation  has  nothing  to  do  with 
the  origin  of  species.  This  form  of  variation 
.  .  .  cannot  even  by  the  most  rigid  and  sus- 
tained selection  lead  to  a  genuine  overstep- 
ping of  the  limits  of  the  species  and  still  less 
to  the  origin  of  new  and  constant  characters." 
"Of  course  every  peculiarity  of  an  organism 
arises  from  a  previously  existing  one;  not, 
however,  by  ordinary  variation,  but  by  a 


126  EVOLUTION 

sudden  thougli  minute  change.  It  is  perhaps 
appropriate  to  compare  such  a  change  with 
a  chemical  substitution." 

"The   name   I   propose   to   give   to   this 

*  species-forming'  variabiHty  is  Mutability 
—  a  term  in  general  use  before  Darwin's  time. 
The  changes  brought  about  by  it,  the  Muta- 
tions, are  phenomena  as  to  the  exact  nature 
of  which  we  understand  very  little  so  far. 
The  best  known  examples  of  such  mutations 
are  the  so-called  spontaneous  variations  (the 

*  single  variations'  of  Darwin)  by  which  new 
and  distinct  varieties  arise.  They  are  also 
termed,  fitly  enough,  sports.  In  spite  of  the 
fact  that  they  occur  fairly  often,  they  are 
usually  not  noticed  until  the  new  form  has 
already  appeared,  when  of  course  it  is  too  late 
to  study  the  phenomenon  of  its  origin  ex- 
perimentally. These  new  forms  can  be 
sought  for  in  cultivated  species,  which  are 
seldom  of  pure  origin;  as  well  as  in  Nature. 
But  as  yet  we  have  no  power  of  inducing  them 
at  will.  It  is  my  belief  that  all  the  simple 
characters  of  animals  and  plants  arise  in  this 
way." 

"Under  the  general  term  variation,  then, 
are  included  two  distinct  phenomena:  muta- 
bility, and  fluctuation  or  ordinary  variation." 

"The  methods  of  artificial  selection  cor- 
respond to  these  two  types  of  variability. 


VARIATION  AND  HEREDITY      127 

Ordinary  variation,  which  is  also  known  as 
individual,  fluctuating  or  gradual  variation, 
is  always  present;  and  it  can  be  described  in 
terms  of  perfectly  definite  laws  which  have 
now  been  fairly  completely  formulated.  It 
provides  the  breeder  with  material  for  his 
improved  races.  On  the  other  hand,  he  has 
to  deal  with  mutations  which  do  not  need 
repeated  selection,  but,  at  the  most,  must  be 
kept  free  from  admixture,  and  which  almost 
always  breed  true  from  the  first." 

In  support  of  his  theory,  Professor  de 
Vries  has  relied  mainly  on  the  sudden  and 
repeated  leaps  and  remarkable  subsequent 
constancy  exhibited  by  the  progeny  of  a 
stock  of  evening  primrose,  (Enothera  la- 
marckiana,  which  he  found  growing  in  a  wild 
state  near  Hilversum  in  Holland.  But  many 
other  instances  of  mutation  are  adduced,  the 
oldest  and  most  accurately  described  being 
the  origin  of  the  cut-leaved  variety  of  the 
greater  celandine,  Chelidonium  ma  jus  lacin- 
iatum,  which  occurred  suddenly  in  1590  in 
the  garden  of  an  apothecary  at  Heidelberg, 
and  has  been  constant  ever  since.  The  evi- 
dence of  mutations  in  the  animal  kingdom  is 
only  beginning  to  be  gathered,  and  there  are 
few  satisfactory  cases  known  outside  of 
experimental  stations.  There  are,  however, 
many  species,  e.g,  of  birds,  which  differ  from 


128  EVOLUTION 

their  relatives  in  features  similar  to  those 
which  arise  as  mutations  in  experimental 
breeding. 

The  issue  at  present  seems  to  be  this.  The 
distinctive  characteristics  of  a  species  may 
arise  in  one  of  two  ways,  either  (1)  by  the 
accumulation  of  fluctuations,  or  (2)  suddenly 
by  mutation.  In  support  of  the  first  theory 
there  are  the  numerous  cases  where  species 
are  connected  by  inter-grades.  In  support 
of  the  second  theory  there  is  experimental 
evidence,  showing  that  many  characteristics 
remain  integral  and  refuse  to  blend.  Patient 
work  will  be  necessary  before  we  can  decide 
as  to  the  relative  importance  of  fluctuations 
and  mutations. 

Mendelism. — One  of  the  most  important 
of  recent  biological  discoveries  has  been  the 
"law  of  heredity,"  stated  in  1865  by  Gregor 
Johann  Mendel  (1822-1884),  an  Austro- 
Silesian  abbot,  who  experimented  for  many 
years  on  crossing  different  varieties  of  garden 
peas.  His  great  paper,  communicated  to  the 
Natural  History  Society  of  Briinn,  remained 
practically  unknown  till  1900,  when  De  Vries 
in  Holland,  Correns  in  Germany,  and  Tscher- 
mak  in  Austria  independently,  and  almost 
simultaneously,  reached  experimxcntal  results 
closely  resembling  Mendel's.  This  led  to  a 
rediscovery  of  the  buried  paper  and  to  a 


VARIATION  AND  HEREDITY      129 

period  of  very  active  experiment,  in  connec- 
tion with  which  Bateson,  Castle,  Cuenot  and 
their  collaborateurs  have  been  especially 
prominent. 

Mendel  worked  chiefly  with  the  edible  pea, 
Pisum  sativum,  which  has  many  well-marked 
varieties  and  is  habitually  self-fertilized. 
When  he  crossed  a  giant  variety  of  6  to 
7  feet  with  a  dwarf  variety,  f  to  1^-  feet 
high,  the  offspring  were  all  tall.  The  charac- 
ter of  tallness  which  appeared  in  the  hybrid 
generation  (F^) ,  to  the  exclusion  of  d warf ness, 
was  called  by  Mendel  the  "dominant" 
character,  the  other  being  "recessive." 

The  tall  cross-bred  peas  were  left  to  self- 
fertilize,  which  corresponds  to  close  inbreed- 
ing in  animals,  and  in  their  progeny  there 
were  tails  and  dwarfs  in  the  average  pro- 
portions of  3: 1. 

When  the  dwarfs  of  this  Fg  generation  were 
allowed  to  self-fertilize,  their  offspring  (Fg) 
were  all  dwarfs,  and  further  generations  bred 
from  them  were  also  all  dwarfs.  They  may 
be  called  pure  recessives,  being  "pure"  as 
regards  dwarfness. 

But  when  the  tails  of  the  Fg  generation  were 
left  to  self -fertilize,  their  offspring  (Fg)  were  of 
two  kinds:  one-third  of  them  (pure  domi- 
nants) produced  tails  only;  two-thirds  of 
them    (impure    dominants)    produced    tails 


130  EVOLUTION 

and  dwarfs  in  the  3  : 1  proportion.  Thus  the 
Fg  generation,  resulting  from  the  self-fertili- 
zation of  the  cross-bred  forms  or  hybrids  (F^), 
consisted  of  25  per  cent,  pure  dominants,  50 
per  cent,  impure  dominants,  and  25  per 
cent,  pure  recessives. 

The  results  may  be  expressed  in  a  scheme : 

Parental  generation  Tall  variety  Dwarf  variety 

I ^1 

First  filial  (hybrid)  all  the  offspring  tall ;  self- 

generation  (Fj)  fertilized  they  yielded 


Second  filial  (inbred)       25%  Tails    _         50%  Tails  25%  Dwarfs 

generation  (Fj)    (pure  dominants)  (impure  dominants)  (pure  recessives) 


A-  ' 


Ta 


25%  50%        25% 

Is      Tails        Tails     Dwarfs       Dwarfs 
(pure)     (impure)  (pure) 


Or,  using  D  for  the  forms  with  the  domi- 
nant character,  R  for  the  forms  with  the  re- 
cessive character,  and  D(R)  for  forms  with 
the  dominant  character  expressed  and  the 
recessive  character  latent,  the  facts  may  be 
expressed  in  a  more  generalized  way  thus 
(after  Punnett) : — • 

Parents  "F1  r'  "  D    R 

First  filial  generation  (Fx)  D(R) 


I  I  I 

ID       +       2D(R)  +        IR 
Second  filial  generation  (F2)            (pure             (impure  (pure 

dominants)      dominants)  recessives) 

I  I  I 

Third  filial  generation  (Fi)  D        ID  +  2D(R)  +  IR        R 

Let  us  take  as  an  illustration  from  among 
animals,  one  lately  well  illustrated  in  the 


VARIATION  AND  HEREDITY      131 

admirable  Evolutionary  Exhibition  of  the 
British  (Natural  History)  Museum.  When 
the  pecuhar  *' waltzing  mice"  are  crossed 
with  normal  mice,  the  offspring  (Fj)  are  all 
normal.  The  waltzing  habit  is  recessive. 
But  when  the  offspring  are  inbred,  their 
progeny  (Fg)  are  normal  mice  and  waltzing 
mice  in  the  proportion  of  3:1.  The  reces- 
sive waltzers  of  this  generation  might  be 
sold  as  pure  waltzers;  with  others  of  their 
kind  they  will  produce  only  waltzers  for  as 
many  generations  as  one  likes  to  breed  them. 
But  the  normals  of  the  same  generation  turn 
out  to  be  of  two  kinds — though  they  are  all 
alike  in  appearance:  one-third  of  them  (pure 
dominants)  will  yield  only  normal  mice;  the 
other  two-thirds  (impure  dominants)  will 
split  up  again,  when  inbred,  into  normal  mice 
and  waltzing  mice  in  the  old  proportions  of 
3:1.  Another  form  of  the  scheme  may  be 
used : — 

Ft  D  (R) 


Ez  '  ID    .'  .2D  (R)    :   IK 


Pa  X>  ID  :  2D  (R) 


:F4    V    T>  -D      JLD  :2D(R) 


13^  EVOLUTION 

It  is  interesting  now  to  inquire  into  the 
occurrence  of  this  remarkable  mode  of  in- 
heritance, which  is  seen  when  the  parent 
forms  have  opposite  or  contrasted  characters 
which  do  not  blend.  The  striking  fact  is  the 
diversity  of  the  organisms  in  which  it  has 
been  demonstrated  in  the  short  period  since 
1900,  e.g.  in  mice,  rats,  rabbits,  guinea-pigs, 
cattle,  poultry,  canaries,  snails,  silk-moths; 
in  beans,  maize,  wheat,  barley,  stocks. 
Another  striking  fact  is  the  great  variety  of 
characters  to  which  it  applies,  e.g.  shades  of 
colour,  peculiarities  of  fur  and  feathers, 
abnormal  features  like  extra  toes,  subtle 
qualities  like  "broodiness"  in  hens,  early 
ripening  or  immunity  to  rust  in  wheat,  and 
so  on. 

Let  us  give  a  few  examples,  arranged  in 
parallel  columns. 

Animals 

Dominant  character.         Recessive  character. 

Hornlessness  in  cattle.  Presence  of  horns. 

Normal  short  hair  in  Long    "Angora" 

rabbits  and  guinea-  hair. 

pigs 

Short  tail  in  Manx  cat  Normal     length     of 

(somewhat      imper-  tail. 

f ectly) . 

Normal  movements  in  Waltzing  in  mice. 

mice. 


VARIATION  AND  HEREDITY      133 


Crest  in  poultry. 
Rose    comb    and    Pea 

comb. 
Extra  toes. 
Broodiness. 


Absence  of  crest. 
Single  comb. 

Normal  four  toes. 
Absence    of    this 

instinct. 
Banded  shell. 


Unbanded  shell   in 
wood-snail. 

Plants 

Dominant  character.      Recessive  character. 

Peas : — 

Tall  stems.  Dwarf  stems. 

Yellow  cotyledons.       Green  cotyledons. 
Brown-skinned  seeds.   White  seeds. 


Round  seeds. 

Wheat: — 

Absence  of  awn. 
Rough  and  red  chaff. 

Keeled  glumes. 
Flinty  endosperm. 
Susceptibility  to 
rust. 

Barley: — 

Two-rowed  ears. 

Nettles: — 


Markedly      dentate 
leaves. 


Wrinkled  seeds. 

Presence  of  awn. 
Smooth    and    white 

chaff. 
Rounded  glumes. 
Floury  endosperm. 
Immunity  to  rust. 


Six-rowed  ears. 

Slightly  dentate 
leaves. 


So  far  we  have  stated  facts — the  results  of 
experiment — but  Mendel  also  suggested  an 


134 


EVOLUTION 


interpretation  or  rationale  of  the  facts.  He 
made  the  supposition  that  the  generative 
cells  or  gametes  produced  by  the  cross-breds 
(Fj)  are  of  two  kinds,  each  kind  bearing  only- 
one  of  the  two  contrasted  or  alternative 
characters,  which,  as  we  have  seen,  do  not 
blend.  He  supposed  also  that  the  two  kinds 
are  produced  in  approximately  equal  num- 
bers. Now  if  each  of  the  hybrids  of  the  Fj 
generation  produces  in  both  sexes  50  per 
cent,  of  its  germ-cells  bearing  the  dominant 
character  and  50  per  cent,  bearing  the  re- 
cessive character,  then,  if  fertilization  be 
fortuitous,  25  per  cent,  of  the  fertilized  egg- 
cells  will  bear  only  the  dominant  character, 
50  per  cent,  will  bear  both  the  dominant  and 
the  recessive  character  (only  the  former  being 
expressed  or  well  expressed  in  development), 
and  25  per  cent,  will  bear  only  the  recessive 
character.  This  is  called  the  theory  of  the 
segregation  of  pure  gametes,  and  it  is  the 
corner-stone  of  Mendelism.  A  scheme  will 
make  it  clearer: — 


I^Iale  Cells. 


Female  Cells. 

©••• 


(r^  '  '  '  (rr\ 


1  pure  dominant 


2  impure  dominants 


1  pure  recessive 


VARIATION  AND  HEREDITY      135 

Mendel's  simple  theory  explains  the  defi- 
nite proportions  ID  +  2D(R)  +  IR,  ob- 
served when  D  and  R  are  crossed.  It  has 
been  tested  in  various  ways,  for  instance,  by 
crossing  D(R)  with  D  or  with  R,  when,  as 
the  hypothesis  demands,  equal  numbers  of 
D(R)  and  D,  or  of  (DR)  and  R,  are  obtained. 

In  his  exceedingly  clear  exposition  of 
Mendehsm  (1905),  Professor  R.  C.  Punnett, 
himself  a  productive  investigator,  states  the 
characteristic  Mendelian  result  thus :  "  Wher- 
ever there  occurs  a  pair  of  differentiating  char- 
acters, of  which  one  is  dominant  to  the  other, 
three  possibilities  exist:  there  are  recessives 
which  always  breed  true  to  the  recessive 
character;  there  are  dominants  which  breed 
true  to  the  dominant  character  and  are  there- 
fore pure;  and  thirdly,  there  are  dominants 
which  may  be  called  impure,  and  which  on 
self-fertilization  (or  inbreeding,  where  the 
sexes  are  separate)  give  both  dominant  and 
recessive  forms  in  the  fixed  proportion  of 
three  of  the  former  to  one  of  the  latter." 

Bringing  the  theoretical  interpretation  into 
prominence — that  is,  the  theory  of  gametic 
segregation.  Professor  Bateson,  the  leader  of 
the  Mendelian  school  in  Britain,  says:  "The 
essential  part  of  the  discovery  is  the  evidence 
that  the  germ-cells  or  gametes  produced  by 
cross-bred  organisms  may  in  respect  of  given 


136  EVOLUTION 

characters  be  of  the  pure  parental  types,  and 
consequently  incapable  of  transmitting  the 
opposite  character;  that  when  such  pure 
similar  gametes  are  united  in  fertilization,  the 
individuals  so  formed  and  their  posterity  are 
free  from  all  taint  of  the  cross;  that  there 
may  be,  in  short,  perfect  or  almost  perfect 
discontinuity  between  these  germs  in  respect 
of  one  of  each  pair  of  opposite  characters." 
This  idea  of  the  segregation  of  the  dominant 
and  the  recessive  characters  in  two  different 
sets  of  germ-cells  is  the  essence  of  Mendelian 
theory. 

Before  passing  from  this  important  and 
fascinating  subject,  we  may  emphasize  two 
points.  There  i^  no  dubiety  in  regard  to  the 
clear  cases  of  Mendelian  inheritance.  Cases 
that  seem  to  be  non-Mendelian  may  turn 
out  to  be  Mendelian — disguised  by  the  com- 
plexity of  the  contrast,  by  interaction  be- 
tween different  pairs  of  characters,  and  by 
what  is  called  incomplete  dominance — but 
there  is  no  mistaking  the  phenomena  of 
Mendelian  inheritance  in  their  typical  ex- 
pression. The  certainty  of  the  matter  is 
evident  from  the  success  with  which  the 
principle  has  already  been  used  in  prediction 
and  in  practice.  On  the  other  hand,  there 
are  also  many  heritable  characters  which 
blend,  and  do  not  conform  to  the  Mendehan 


VARIATION  AND  HEREDITY      137 

mode  of  inheritance.  In  illustration  we 
may  refer  to  hybrid  trout,  half-bred  sheep, 
and  mulattoes. 

Application  to  Evolution  Theory. — 
Like  Weismannism,  which  has  for  one  of  its 
foundations  the  idea  of  germinal  continuity, 
Mendelism  conceives  of  the  hereditary  rela- 
tion in  the  strict  sense,  i.e.  not  as  between  the 
bodies  of  parent  and  offspring,  but  between 
the  parental  and  the  filial  germ-cells. 

Like  Weismannism,  which  has  for  another 
of  its  foundations  the  idea  of  determinants 
or  representative  particles  constituting  the 
mosaic  of  inheritance,  Mendelism  regards  the 
organism  as  built  up  of  a  number  of  definite, 
separably  heritable  characters. 

Mendelism  has  thrown  light  on  at  least 
certain  kinds  of  variation,  those  which  are 
due  to  the  addition  or  omission  of  one  or  more 
definite  elements.  As  Bateson  puts  it: 
"With  the  development  of  the  inquiry  it  has 
become  clear  that  variation,  in  so  far  as  it 
consists  in  the  omission  of  elementary  fac- 
tors, is  the  consequence  of  a  process  of  *  un- 
packing.' The  white  sweet  pea  was  created 
in  the  variation  by  which  one  of  the  colour- 
factors  was  dropped  out.  Such  variation  is 
not,  as  it  was  formerly  supposed  that  all 
variation  must  be,  a  progress  from  a  lower 
degree  of  complexity  to  a  higher,  but  the 


138  EVOLUTION 

converse.  When  from  a  single  wild  type 
man  succeeds  in  producing  a  multitude  of 
new  varieties,  we  may  speak  of  the  result  as 
a  progress  in  differentiation:  but  we  must 
recognize  that  the  term  is  only  applicable 
loosely,  and  that  the  obvious  appearance  of 
increased  complexity  may  in  reality  be  the 
outcome  of  a  process  of  simplification." 
Similarly,  "reversion  occurs  when  the  sum 
total  of  the  factors  returns  to  that  which  it 
has  been  in  some  original  type."  The  re- 
turn may  be  brought  about  by  the  omission 
of  an  element  or  by  the  addition  of  a  missing 
element.  If  certain  kinds  of  variation  may 
be  called  "unpacking,"  reversion  is  re- 
packing. 

In  discussing  the  bearing  of  Mendelism  on 
the  theory  of  evolution,  Bateson  makes  three 
important  suggestions.  (1)  "One  has  only 
to  glance  over  trays  of  birds'  skins,  the  port- 
folios of  a  herbarium,  or  drawers  of  butter- 
flies and  moths,  to  discover  abundant '  species ' 
which  are  analytical  varieties  of  others,"  i.e. 
differing  in  the  presence  or  absence  of  defi- 
nite factors.  "The  principles  of  heredity  we 
trace  in  our  experimental  breeding  are  operat- 
ing throughout  the  natural  world  of  species." 
(2)  The  fact  of  discontinuity  in  variation, 
whether  it  be  called  mutation  or  something 
else,  is  undoubted,  but  hitherto  there  has 


VARIATION  AND  HEREDITY       139 

been  "nothing  to  indicate  how  or  when  it  was 
determined.  We  now  see  that  the  discon- 
tinuous variations  are  in  the  main  the  out- 
ward manifestations  of  the  presence  or  ab- 
sence of  corresponding  Mendelian  factors, 
and  we  recognize  that  the  unity  of  these 
factors  is  a  consequence  of  the  mode  in  which 
they  are  treated  by  the  cell-divisions  of 
gameto-genesis."  (3)  "The  notion  that  a 
character  once  appearing  in  an  individual  is 
in  danger  of  obliteration  by  the  inter-crossing 
of  that  individual  with  others  lacking  that 
character  proves  to  be  unreal;  because  in  so 
far  as  the  character  depends  on  factors  which 
segregate,  no  obliteration  takes  place.  The 
factors  are  permanent  by  virtue  of  their  own 
properties,  and  their  permanence  is  not 
affected  by  crossing .  .  .  .  "  Moreover,  he 
continues,  "The  conception  of  Evolution  as 
proceeding  through  the  gradual  transforma- 
tion of  masses  of  individuals  by  the  accumu- 
lation of  impalpable  changes  is  one  that  the 
study  of  genetics  shows  immediately  to  be 
false.  Once  for  all,  that  burden  so  gratui- 
tously undertaken  in  ignorance  of  genetic 
physiology  by  the  evolutionists  of  the  last 
century  must  be  cast  into  oblivion.  For  the 
facts  of  heredity  and  variation  unite  to 
prove  that  genetic  variation  is  a  phenomenon 
of    individuals.      Each    new    character    is 


140  .         EVOLUTION 

formed  in  some  germ-cell  of  some  particular 
individual,  at  some  point  of  time." 

The  issue  at  present  seems  to  be  this,  that 
there  are  characters  which  blend  when 
crossed,  and  others  which  segregate  when 
crossed.  Patient  work  is  necessary  in  order 
to  test  these  two  groups  and  to  discover  what 
is  the  criterion  of  blending  and  alternating 
respectively.  In  his  interesting  work  on 
*' Hereditary  Characters,"  Dr.  Charles  E. 
Walker  maintains  the  thesis  that  racial 
characters  tend  to  blend  and  that  individual 
characters  are  transmitted  in  an  alternative 
or  Mendelian  manner. 

Origin  of  Variations. — Since  variations 
form  the  raw  materials  of  evolution,  it 
would  be  satisfactory  if  we  could  conclude 
this  chapter  by  stating  how  they  arise.  But 
that  is  quite  impossible  at  present.  We 
know  very  little  that  is  certain  in  regard  to 
the  originative  factors  in  evolution.  We 
must  still  confess,  with  Darwin:  "Our 
ignorance  of  the  laws  of  variation  is  pro- 
found." It  may  be  of  interest,  however,  to 
notice  some  of  the  suggestions  that  have 
been  made  in  regard  to  this  fascinating 
problem. 

There  are  variations  which  mean  augmen- 
tation, or  diminution,  or  re-arrangement  of 
already    existing    qualities.      Now,    if    the 


VARIATION  AND  HEREDITY       141 

hereditary  qualities  are  carried  by  represent- 
ative particles  in  the  germ-cells,  we  can  in  a 
measure  understand  the  origin  of  the  kind 
of  variation  referred  to;  for  extraordinarily 
intricate  permutations  and  combinations  go 
on  in  the  microcosm  of  the  germ-cells. 
Particularly  in  the  process  of  maturation  is 
there  what  we  might  call  a  shuffling  of  the 
cards — even  a  throwing  away  of  half  of  the 
pack.  In  fertilization,  again,  paternal  and 
maternal  contributions  form  a  new  unity. 
Perhaps  there  may  be,  as  Weismann  sup- 
poses, a  struggle  between  rival  hereditary 
items. 

But  there  seems  to  be  another  kind  of 
variation,  qualitative  rather  than  quantita- 
tive, substantive  rather  than  architectural, 
when  something  distinctively  new  appears. 
What  can  be  said  as  to  their  origin?  Weis- 
mann has  suggested  that  the  oscillations  and 
changes  in  the  blood  and  other  nutritive 
fluids  may  stimulate  the  germ-plasm  to  a  new 
departure.  It  may  also  be  that  important 
changes  in  the  environment  may  saturate 
through  the  body  and  provoke  the  germ- 
plasm    to    vary.     There    are   other   "may 

he's." 

With  all  recognition  and  appreciation  of 
the  work  and  thought  above  summarized, 
we  cannot  but  think  that  the  secret  of  varia- 


142  EVOLUTION 

bility  lies  yet  deeper,  in  the  very  nsCture  of 
the  Hving  organism  itself.  It  has  been  a 
Proteus  from  the  first;  changefulness  is  its 
most  abiding  quahty;  in  short,  the  essence 
of  the  creature  is  its  innate  creativeness. 


CHAPTER  V 

SELECTION 

Huxley  on  "The  Quintessence  of  Darwinism" — Analj'tic 
Abstract  of  "The  Origin  of  Species"  (Variation  under 
Domestication  —  Artificial  Selection  —  Variation  under 
Natural  Conditions  —  Struggle  for  Existence  —  Natural 
Selection) 

The  Case  for  Natural  Selection — Direct  Evidence  of  Natural 
Selection — Implications  of  the  Concept  of  Natural  Selec- 
tion— Different  Kinds  of  Selection  (Sexual  Selection  — ■ 
Germinal  Selection) — Family  and  Group  Selection — Auxil- 
iary Hypothesis  of  Isolation — Eugenics  as  a  Renewal  of 
Evolution. 

Darwin's  achievement  in  "The  Origin  of 
Species"  was  twofold.  In  the  first  p'ace, 
he  presented  the  evidences  of  the  fact  of 
evolution  so  forcibly  and  so  fairly  that  he 
made  evolutionists  of  the  great  majority  of 
his  readers.  Indeed,  he  made  the  world 
"think  in  terms  of  evolution."  In  the  second 
place,  in  his  theory  of  Nature's  sifting  of 
hereditary  variations  he  gave  a  causal  inter- 
pretation of  the  age-long  process  of  Becoming. 
He  made  the  evolution  idea  current  intellec- 
tual coin;  but  his  success  tn  making  the  fact 
clear  and  credible  was  in  part  due  to  his 
discovery  of  one  of  the  chief  factors. 

143 


144  EVOLUTION 

Huxley  on  "The  Quintessence  of 
Darwinism."  — Huxley  made  this  distinc- 
tion between  fact  and  factors  very  plain  in 
his  essay  "On  the  Reception  of  the  Origin 
of  Species"  in  Darwin's  "Life  and  Letters." 
He  first  states  the  grounds  of  his  own 
agnostic  position  (up  to  1858)  with  respect 
to  the  doctrine  of  evolution  as  promulgated 
by  Lamarck,  Robert  Chambers,  and  even 
Spencer:  "Firstly,  that  up  to  that  time  the 
evidence  in  favour  of  transmutation  was 
wholly  insufficient;  and,  secondly,  no  sug- 
gestion respecting  the  causes  of  the  trans- 
mutation assumed,  which  had  been  made, 
was  in  any  way  adequate  to  explain  the 
phenomena." 

He  goes  on  to  say: — 

"The  suggestion  that  new  species  may 
result  from  the  selective  action  of  external 
conditions  upon  the  variations  from  their 
specific  type  which  individuals  present — and 
which  we  call  "spontaneous"  because  we 
are  ignorant  of  their  causation — is  as  wholly 
unknown  to  the  historian  of  scientific  ideas 
as  it  was  to  biological  specialists  before  1858. 
But  that  suggestion  is  the  central  idea  of  the 
'Origin  of  Species,'  and  contains  the  quin- 
tessence of  Darwinism.  .  .  .  That  which  we 
were  looking  for,  and  could  not  find,  was  an 
hypothesis  respecting  the  origin  of  known 


SELECTION  145 

organic  forms  which  assumed  the  operation 
of  no  causes  but  such  as  could  be  proved 
to  be  actually  at  work.  We  wanted,  not  to 
pin  our  faith  to  that  or  any  other  speculation, 
but  to  get  hold  of  clear  and  definite  concep- 
tions which  could  be  brought  face  to  face 
with  facts  and  have  their  validity  tested. 
The  *  Origin'  provided  us  with  the  working 
hypothesis  we  sought.  ..." 

Of  "the  quintessence  of  Darwinism,"  then, 
a  brief  account  is  needed,  and  this  mav  be 
best  given  by  following  as  closely  as  possible 
upon  the  lines  of  the  magnum  opus  itself, 
although  the  full  title  of  this— "The  Origin 
of  Species  by  means  of  Natural  Selection,  or 
the  Preservation  of  Favoured  Races  in  the 
Struggle  for  Life,"  is  its  own  best  and 
briefest  summary. 

Analysis  of  "The  Origin  of  Species." 
— After  mentioning  that  his  first  light  upon 
the  origin  of  species  was  derived  from  his 
early  distributional  studies,  Darwin  points 
out  that  "a  naturalist,  reflecting  on  the 
mutual  affinities  of  organic  beings,  on  their 
embryological  relations,  their  geographical 
distribution,  geological  succession,  auvd  such 
other  facts,  might  come  to  the  conclusion 
that  species  had  not  been  independently 
created,  but  had  descended  like  varieties 
from   other   species.      Nevertheless,   such   a 


146  EVOLUTION 

conclusion,  even  if  well  founded,  would  be 
unsatisfactory  unless  it  could  be  shown  how 
the  innumerable  species  inhabiting  this  world 
have  been  modified  so  as  to  acquire  that  per- 
fection of  structure  and  co-adaptation  which 
justly  excites  our  admiration."  Again,  "It 
is  therefore  of  the  highest  importance  to 
gain  a  clear  insight  into  the  means  of  modi- 
fication and  co-adaptation.  At  the  com- 
mencement of  my  observations  it  seemed  to 
me  probable  that  a  careful  study  of  domesti- 
cated animals  and  cultivated  plants  would 
offer  the  best  chance  of  making  out  this 
obscure  problem.  Nor  have  I  been  disap- 
pointed: in  this  and  in  all  other  perplex- 
ing cases  I  have  invariably  found  that  our 
knowledge,  imperfect  though  it  be,  of  varia- 
tion under  domestication  affords  the  best 
and  safest  clue."  It  was  therefore  with 
variation  under  domestication  that  he  began 
his  book. 

Variation  under  Domestication. — A 
comparison  between  the  individuals  of  a  cul- 
tivated or  domesticated  "variety"  shows  a 
greater  degree  of  variation  than  there  ob- 
tains between  the  individuals  of  a  wild 
species  or  "variety."  The  higher  variability 
of  domestic  productions  is  to  be  ascribed  to 
the  less  uniform  conditions  of  their  up- 
bringing, perhaps  in  part  to  excess  of  food. 


SELECTION  147 

Exposure  to  new  conditions  must  be  con- 
tinued for  generations  to  set  up  any  groat 
variation;  but  this,  once  set  up,  continues 
indefinitely.  Changed  conditions  may  di- 
rectly influence  the  whole  organization  of 
the  creature  or  certain  parts  alone;  or  they 
may  act  indirectly  through  the  reproductive 
system.  With  respect  to  the  direct  action, 
the  nature  of  the  organization  seems  to 
count  for  more  than  that  of  the  conditions. 
The  effect  on  the  offspring  may  be  definite: 
e.g,  size  may  depend  upon  the  amount  of 
food,  colour  upon  quality  of  food,  thickness 
of  skin  and  hair  upon  climate,  etc.  But 
indefinite  variability  is  a  much  commoner 
result  of  changed  conditions,  and  has  prob- 
ably played  a  more  important  part  in  the 
formation  of  our  domestic  races.  The  re- 
productive system  is  peculiarly  sensitive  to 
very  slight  external  changes.  Many  plants 
and  animals  will  not  reproduce  in  domesti- 
cation, even  though  individually  vigorous; 
others,  though  weak  and  sickly,  breed  freely. 
Hence  we  need  not  be  surprised  at  the 
reproductive  system  acting  irregularly  and 
producing  variations.  But  that  variation  is 
not  exclusively  associated  with  sexual  re- 
production is  demonstrated  by  the  case  of 
plants  "sporting"  through  bud- variation. 
Such  cases,  moreover,  prove  that  the  nature 


148  EVOLUTION 

of  the  organism  counts  for  more  than  the 
conditions. 

Changed  habits,  e.g.  changes  in  the  de- 
gree of  use  or  disuse  of  a  part,  produce  an 
inherited  effect,  witness  the  lighter  wing- 
bones  and  heavier  leg-bones  of  the  domestic 
duck,  or  the  enlarged  udders  of  cows. 

Variations  are  often  definitely  correlated: 
thus  short-beaked  pigeons  have  small  feet; 
hairless  dogs  have  imperfect  teeth;  and 
blue-eyed  white  tom-cats  are  deaf.  Hence 
selection  of  any  one  character  will  prob- 
ably modify  others  indirectly. 

Although  the  laws  of  inheritance  are 
mostly  unknown,  it  seems  that  probably 
most,  if  not  all,  characters  tend  to  be  in- 
herited. There  is  no  satisfactory  evidence 
to  support  the  popular  idea  that  domestic 
varieties  revert  to  the  primitive  stock  when 
they  run  wild.  Reversions  occasionally 
occur  in  domestication,  but  there  is  no  gen- 
eral tendency  to  lose  what  has  been  gained 
- — apart,  of  course,  from  breeding  with  wild 
stocks,  or  with  other  domesticated  ones. 

Except  in  being  less  uniform  than  natural 
species,  in  often  differing  more  widely  in  a 
single  part,  and  in  being  fertile  when  crossed, 
there  are  no  well-marked  distinctions  be- 
tween our  domestic  races  and  the  so-called 
true  species  of  a  genus.    The  many  breeds  of 


SELECTION  119 

dogs  and  cattle  may  have  arisen  from  more 
than  one  species;  but  probably  those  of 
horses  and  fowls,  and  clearly  those  of  rabbits, 
ducks  and  pigeons,  are  each  descended  from 
a  single  wild  species.  At  least  a  score  of 
varieties  of  pigeon  might  be  chosen  which 
differ  so  thoroughly,  internally  as  well  as 
externally,  that  an  ornithologist,  treating 
them  as  wild  birds,  would  be  compelled  to 
grant  them  specific,  and  even  distinct  ge- 
neric rank.  Yet,  since  all  these  have  indis- 
putably arisen  from  the  wild  rock-dove,  it 
is  clear  that  naturalists  who  admit  a  unity 
to  such  domestic  races,  which  professed 
breeders  have  often  laughed  to  scorn,  should 
in  turn  be  cautious  before  deriding  the  unity 
of  wild  ones. 

Artificial  Selection. — How,  then,  have 
domestic  races  been  produced?  By  external 
conditions  or  habits  alone  .^^  One  of  their 
tell-tale  features  is  in  exhibiting  adaptations, 
not  to  their  own  good,  but  to  man's  use  or 
fancy.  We  know  that  all  the  breeds  were 
not  produced  in  their  present  state  of  per- 
fection, and  the  key  is  man's  accumulative 
selection.  Nature  gives  successive  variations ; 
man  adds  them  up,  making  for  himself  use- 
ful breeds.  Skilful  breeders  speak  of  the 
organization  as  plastic  and  under  control, 
and  have  effected  great  changes  within  our 


150  EVOLUTION 

own  generation.  Unconscious  selection, 
which  results  from  every  one  trying  to 
possess  and  breed  the  best  individuals,  is 
even  more  important.  The  accumulation  of 
change  which  man  effects  explains  why  we 
so  often  cannot  recognize  the  wild  parent 
stocks  of  our  cultivated  plants,  while  its 
absence  in  countries  inhabited  by  uncivilized 
man  explains  why  these  never  yield  plants 
worth  immediate  culture.  Man's  power  of 
selection  is  facilitated  by  keeping  large  num- 
bers, in  which  variations  are  more  likely  to 
occur.  Facility  in  preventing  crosses  is 
also  of  importance,  e.g,  in  the  case  of  pigeons 
as  contrasted  with  cats;  some  species  are, 
however,  less  variable  than  others,  e.g.  the 
goose. 

Variation  under  Natural  Conditions. 
— Individual  differences  arise  even  in  the 
offspring  of  the  same  parents  and  tend  to 
be  inherited;  hence  they  afford  material  for 
natural  selection  to  act  on  and  accumulate, 
precisely  as  they  would  for  human  selection. 
(It  may  be  that  genera  with  large  num- 
bers of  slightly  different  species — e.g.  rose, 
bramble  and  hawkweed — owe  their  protean 
character  to  their  variations  being  of  no 
service  or  disservice,  and  consequently  not 
being  acted  on  by  natural  selection.)  In 
determining  whether  groups  of  similar  forms 


SELECTION  151 

should  be  ranked  as  species  or  as  varieties, 
the  opinion  of  naturalists  of  sound  judg- 
ment and  wide  experience  is  the  only  guide, 
yet  this  lacks  unanimity:  for  example,  of 
the  polymorphic  genera  {i.e.  rich  in  species 
with  a  small  range  of  differences)  in  the 
British  flora  alone,  Bentham  reckons  112 
species,  but  Babington  251.  Wallace  has 
shown  that  no  certain  criterion  can  be  given 
by  which  to  define  his  own  convenient  work- 
ing categories  of  Malayan  butterflies  and 
moths,  viz.  variable  forms,  local  forms,  sub- 
species, and  representative  species.  As  De 
Candolle  concluded  from  his  monograph  on 
oaks  (in  which  he  shows  at  least  two-thirds 
of  his  300  species  to  be  provisional),  "so 
long  as  a  genus  is  imperfectly  known  and 
its  species  founded  upon  a  few  specimens" 
they  seem  clearly  limited;  but,  "just  as  we 
come  to  know  them  better,  intermediate 
forms  flow  in  and  doubts  as  to  specific  limits 
augment."  The  terms  variety  and  species 
are  thus  arbitrarily  applied  to  indefinable 
groups  of  more  or  less  closely  similar  in- 
dividuals. Common  species  that  range  wide 
and  are  much  diffused  are  those  which  vary 
most.  The  species  of  the  larger  genera  in 
each  country  vary  more  frequently  than  the 
species  of  the  smaller  genera.  The  species 
of  large  genera  present  strong  analogies  with 


152  EVOLUTION 

varieties,  which  suggests  that  they  origi- 
nated as  such. 

Struggle  for  Existence. — The  term 
"struggle  for  existence"  is  used  in  a  large 
and  metaphorical  sense,  including  depend- 
ence of  one  being  upon  another,  and  em- 
bracing (which  is  more  important)  not  only 
the  life  of  the  individual,  but  success  in 
leaving  progeny.  From  the  high  (geo- 
metrical) rate  of  increase  of  all  organic  be- 
ings (even  the  slow  breeders  requiring  only 
a  few  more  years  to  people  a  whole  district) 
struggle  inevitably  follows,  either  one  in- 
dividual with  another  of  the  same  species, 
or  with  the  individuals  of  a  distinct  species, 
or  with  the  physical  conditions  of  life.  It  is 
the  doctrine  of  Malthus  applied  with  mani- 
fold force  to  the  entire  animal  and  vegetable 
kingdoms,  for  in  this  case  there  can  be  no 
artificial  increase  of  food  and  no  prudential 
restraints  from  marriage. 

The  checks  to  increase  are  very  obscure. 
Eggs  or  young  animals  generally  suffer  most, 
and  plants,  mostly  as  seedlings,  both  from 
germinating  on  ground  already  occupied  and 
from  animals.  The  amount  of  food,  of 
course,  gives  the  extreme  limit  of  numbers; 
very  frequently,  however,  the  check  is 
given  by  the  attacks  of  enemies,  as  on  game 
by  "vermin."     Changes  of  climate  play  an 


SELECTION  153 

important  part,  and  periodical  seasons  of 
extreme  cold  have  destroyed  as  many  as  four- 
fifths  of  the  bird  of  an  observed  area.  Epi- 
demics, too,  may  occur.  In  many  a  species 
a  large  stock  of  individuals  is  often  essential 
to  its  continuance. 

Complex  and  unexpected  checks  and  re- 
lations exist  between  organic  beings  which 
have  to  struggle  together;  witness  the  pro- 
found alteration  of  the  flora  and  fauna  of  a 
heath  when  planted  with  Scots  pine,  these 
again  being  wholly  dependent  upon  the  ex- 
clusion of  cattle.  But  in  several  parts  of 
the  world  insects  determine  the  existence  of 
cattle.  Again,  red  clover  depends  for  fertil- 
ization upon  the  humble-bees,  these  upon 
immunity  from  the  attacks  of  field-mice,  and 
thus  indirectly  upon  the  number  of  cats. 
Hence  no  bees,  no  clover,  and  the  more  cats, 
the  more  clover. 

The  struggle  will  almost  invariably  be 
most  severe  between  the  individuals  of  the 
same  species,  for  they  frequent  the  same 
districts,  require  the  same  food,  and  are  ex- 
posed to  the  same  dangers.  In  the  case  of 
varieties  of  the  same  species,  the  struggle 
will  generally  be  almost  equally  severe,  and 
we  sometimes  see  the  contest  soon  decided 
(as  in  the  case  of  varieties  of  wheat  or  of 
sweet  pea,  of  the  mountain  sheep  or  of  the 


154  EVOLUTION 

medicinal  leech).  Similarly,  the  struggle  be- 
tween species  of  the  same  genus  will  generally 
be  more  severe  than  between  the  species  of 
distinct  genera.  This  is  illustrated  by  the 
inevitable  replacement  of  the  black  rat  by 
the  brown,  or  of  the  large  cockroach  by  the 
small.  The  structure  of  every  organism 
is  related  to  that  of  all  others  with  which 
it  competes,  from  which  it  escapes,  or  on 
which  it  preys;  witness  alike  the  teeth 
and  talons  of  the  tiger,  or  the  legs  and 
claws  of  the  parasite  clinging  to  his  hair. 
The  albumen  of  a  seedling  favours  its  strug- 
gle with  plants  already  growing  around  it. 
Darwin  goes  on  to  speak  of  two  "canine 
animals"  struggling  with  each  other  in  a 
time  of  dearth;  of  mistletoe  versus  mistletoe 
on  the  same  branch ;  of  mistletoe  versus  other 
fruit-bearing  plants;  of  a  plant  on  the  edge 
of  the  desert  in  days  of  drought;  and  then 
says,  "  In  these  several  senses,  which  pass 
into  each  other,  I  use,  for  convenience'  sake, 
the  general  term  of  Struggle  for  Existence." 
Natural  Selection. — How  will  this 
struggle  for  existence  act  in  regard  to  varia- 
tion .^^  Can  the  principle  of  selection,  so  po- 
tent in  the  hands  of  man,  apply  under 
Nature .f^  Most  efficiently;  for,  when  we  bear 
in  mind  the  constant  occurrence  of  variation, 
with  the  strength  of  the  hereditary  tendency. 


SELECTION  155 

also  how  infinitely  close  and  complex  are  the 
mutual  relations  of  organic  beings  to  each 
other  and  to  their  physical  conditions  of  life, 
and  consequently  what  infinitely  varied 
diversities  of  structure  might  be  of  use  to 
each  being  under  changing  conditions  of  life, 
can  it  be  thought  improbable,  seeing  that 
variations  useful  to  man  have  undoubtedly 
occurred,  that  other  variations,  useful  in 
some  way  to  each  being  in  the  great  and 
complex  battle  of  life,  should  occur  in  the 
course  of  many  generations?  And  if  such  do 
occur,  can  we  doubt  (remembering  that  many 
more  individuals  are  born  than  can  possibly 
survive)  that  individuals  having  any  ad- 
vantage, however  slight,  over  their  fellows 
would  have  the  best  chance  of  surviving  and 
of  procreating  their  kind?  On  the  other 
hand,  we  may  feel  sure  that  any  variation  in 
the  least  degree  injurious  would  be  inevi- 
tably destroyed. 

This  preservation  of  favourable  and  this 
destruction  of  injurious  variations  are  called 
natural  selection,  or,  less  metaphorically,  the 
survival  of  the  fittest,  the  one  term  referring 
mainly  to  the  process,  the  other  to  the  result. 
The  probable  course  of  natural  selection  may 
be  understood  from  the  case  of  a  country 
undergoing  change  of  climate.  The  pro- 
portional numerical  strengths  of  its  species 


156  EVOLUTION 

will  be  changed;  some  will  probably  become 
extinct;  and  these  changes  will  seriously 
affect  the  others.  Immigration  of  new  forms 
might  also  occur,  with  further  serious  dis- 
turbance; or,  where  this  is  impossible,  there 
will  be  places  in  the  economy  of  Nature 
which  might  be  better  filled  up.  In  such 
cases  slight  changes  in  structure  or  habit 
which  in  any  way  favoured  the  individuals 
of  any  species,  by  adapting  them  better  to 
their  altered  conditions,  would  tend  to  be 
preserved,  and  natural  selection  would  have 
free  scope  for  its  work  of  improvement. 
Moreover,  changed  conditions  increase  varia- 
bility. 

As  man  produces  great  results  by  his 
artificial  selection,  what  may  not  natural 
selection  effect?  Man  selects  only  for  his 
own  purposes.  Nature  for  the  good  of  the 
creature  itself;  man  on  the  more  external 
characters  (he  has  become  more  adventurous 
since  Darwin's  day).  Nature  on  the  whole 
machinery  of  life;  man  irregularly  and  im- 
perfectly for  a  short  time.  Nature  by  con- 
sistent accumulation  during  whole  geological 
periods.  Natural  selection  is  daily  and 
hourly  scrutinizing,  throughout  the  world, 
the  slightest  variations,  rejecting  those  that 
are  bad,  preserving  and  adding  up  all  that  are 
good,  silently  and  insensibly  working,  when- 


! 


SELECTION  157 

ever  and  wherever  opportunity  offers,  at  the 
improvement  of  each  organic  being  in  relation 
to  its  animate  and  inanimate  conditions  of 
life.  It  may  operate  on  characters  which 
we  are  apt  to  consider  of  very  trifling  im- 
portance, and  its  accumulation  of  small 
variations  may  set  up  unexpected  correlative 
changes.  It  may  affect  the  egg,  the  seed,  or 
the  young  as  easily  as  the  adult;  it  may  adapt 
the  structure  of  young  to  parent  and  of 
parent  to  young;  and  in  social  animals  it  may 
adapt  the  structure  of  each  for  the  benefit 
of  all.  In  the  later  editions  of  the  "Origin" 
a  brief  account  of  sexual  selection  is  given 
at  this  point. 

The  theory  of  natural  selection  is  then 
illustrated  by  particular  instances.  Thus 
Darwin  pictures  the  formation  of  swift 
varieties  of  wolves,  much  in  the  same  way 
as  greyhounds  have  been  evolved  by  man. 
Or,  again,  he  refers  to  the  secretion  of 
nectar  by  flowers,  its  use  to  insects,  the 
action  of  these  in  carrying  the  fertilizing 
pollen,  its  advantage  in  intercrossing,  and  the 
resultant  finely  adjusted  adaptation  of  flower 
and  insect  to  each  other  through  the  pres- 
ervation of  their  respective  advantageous 
variations. 

Circumstances  favourable  for  the  pro- 
duction of  new  forms  through  natural  selcc- 


158  EVOLUTION 

tion  are  great  variability,  large  numbers  of 
individuals,  the  complex  effects  of  inter- 
crossing, isolation  in  confined  areas  (yet 
probably  still  more  an  extension  over  con- 
tinental areas,  especially  if  oscillating  in 
level),  and  considerable  lapse  of  time.  But 
the  lapse  of  time  by  itself  must  not  be  sup- 
posed to  do  anything  (as  if  the  forms  of  life 
were  undergoing  change  by  some  innate 
law),  but  merely  to  afford  increased  oppor- 
tunity for  variation  and  environmental 
change.  Extinction,  to  which  rare  species 
are  on  the  way,  is  the  last  word  of  natural 
selection. 

The  divergence  of  character  brought  about 
by  artificial  selection  in  domestic  breeds  is 
efficiently  paralleled  in  Nature,  since  the 
more  diversified  the  offspring  of  each  species, 
the  more  they  will  seize  on  diverse  places  in 
the  economy  of  Nature,  and  so  increase  in 
numbers.  The  greatest  amount  of  life  can 
be  supported  by  increased  diversification  of 
structure,  each  species  being  adapted  to  a 
particular  set  of  conditions.  This  divergence 
of  character,  with  extinction  of  intermediate 
forms,  explains  the  difficulties  of  classification 
— of  making  a  genealogical  tree  which  will 
express  the  facts  of  the  case  and  represent 
diagrammatically  "the  great  tree  of  life, 
which  fills  with  its  dead  and  broken  branches 


SELECTION  159 

the  crust  of  the  earth  and  covers  tlic  sur- 
face with  its  ever-branching  and  beautiful 
ramifications. " 

Darwin's  Summary. — The  preceding  sum- 
mary of  the  classical  statement  of  the  doc- 
trine of  natural  selection  should  be  supple- 
mented by  reference  not  only  to  the  original 
work,  to  the  corroborative  labours  of  its 
author,  to  the  able  independent  treatise 
("Natural  Selection")  of  Wallace,  and  to  the 
synthetic  treatments  of  the  whole  subject  of 
evolution  given  by  Haeckel  in  his  "Generelle 
Morphologic,"  and  by  Spencer  in  his  "Prin- 
ciples of  Biology, "  but  to  the  enormous  mass 
of  exposition,  argument  and  illustration 
accumulated  by  subsequent  writers,  com- 
mencing with  Hooker  and  Asa  Gray,  Huxley 
and  Haeckel,  but  soon  becoming  too  numer- 
ous for  mention.  We  indicate,  however, 
a  few  convenient  recent  summaries  in  the 
"Bibliography"  at  the  close  of  this  volume. 

But  while  we  must  avoid  the  error  of  sup- 
posing that  the  last  word  on  natural  selection 
was  said  by  Darwin,  or  that  there  is  not  still 
abundant  opportunity  both  for  reflection 
and  research  in  regard  to  it,  we  must  be 
clear  as  to  the  essential  simplicity  of  the 
general  theory.  Darwin  himself  summed  it 
up  in  a  couple  of  sentences:  "As  many  more 
individuals  of  each  species  are  born  than  can 


160  EVOLUTION 

possibly  survive,  and  as,  consequently,  there 
is  frequently  recurring  struggle  for  existence, 
it  follows  that  any  being,  if  it  vary  however 
slightly  in  any  manner  profitable  to  itself, 
under  the  complex  and  sometimes  varying 
conditions  of  life,  will  have  a  better  chance 
of  surviving,  and  thus  be  naturally  selected. 
From  the  strong  principle  of  inheritance 
any  selected  variety  will  tend  to  propagate 
its  new  and  modified  form." 

There  are  here  three  main  propositions: — 

(1)  Variability  is  a  fact  of  life.  Variations 
are  of  frequent  occurrence,  and  some  of  them 
are  certainly  transmissible. 

(2)  Living  creatures  are  very  prolific.  The 
majority  die  young.  There  is  a  ceaseless 
struggle  for  existence  and  the  web  of  inter- 
relations is  such  that  even  minute  variations 
may  determine  survival. 

(3)  If  variations  occur  in  the  direction  of 
increased  fitness,  if  the  variations  are  trans- 
missible, and  if  there  is  discriminate  selection 
with  reference  to  these  variations,  then  the 
possessors  of  the  fitter  variations  are  bound 
to  be  favoured  with  longer  life  and  larger 
families — with  survival,  in  short.  If  this  is 
kept  up  consistently,  then  new  adaptations 
and,  probably  with  the  help  of  some  form  of 
isolation,  new  species,  will  arise. 

The  Case  for  Natural  Selection. — The 


SELECTION  IGl 

theory  of  natural  selection  has  the  marks  of 
a  good  theory — it  works  well  as  an  interpre- 
tative formula  in  the  most  varied  cases,  it 
has  proved  itself  a  useful  instrument  of 
research,  and  it  has  even  been  made  the 
basis  of  successful  prediction.  Darwin  him- 
self was  under  no  misapprehension  as  to  the 
logical  position  of  his  theory — that  its 
strength  was  in  its  interpretative  value,  not 
in  its  direct  evidence.  In  a  letter  to  Bentham 
in  1863,  he  writes:  "The  belief  in  natural 
selection  must  at  present  be  grounded  en- 
tirely on  general  considerations — (1)  on  its 
being  a  vera  causa,  from  the  struggle  for 
existence  and  the  certain  geological  fact 
that  species  do  somehow  change;  (2)  from 
the  analogy  of  change  under  domestication 
by  man's  selection;  (3)  and  chiefly  from  this 
view  connecting  under  an  intelligible  point 
of  view  a  host  of  facts."  Given  variability, 
a  high  rate  of  increase,  the  struggle  for 
existence,  the  web  of  life,  the  observed  fact 
that  most  living  creatures  die  young — it 
seems  to  most  naturalists  to  follow  that 
natural  selection  is  indeed  a  vera  causa 
and  the  survival  of  the  fittest  a  reality. 

Direct  Evidence  for  Natural  Selec- 
tion.— One  of  the  interesting  steps  of  prog- 
ress since  Darwin's  day  has  been  the 
attempt  to  secure  definite  evidence  of  the 


162  EVOLUTION 

operation  of  natural  selection.  The  theory 
works  well  as  an  interpretation,  but  what 
we  need  is  actual  proof  of  discriminate 
selection,  actual  evidence  that  survivors 
do  survive  in  virtue  of  particular  qualities. 
A  few  examples  of  this  in  present-day  ex- 
perience will  give  strength  to  the  belief  that 
similar  processes  occurred,  as  Darwin  sug- 
gested, throughout  the  past. 

It  is  interesting  to  note  that  so  strong 
a  selectionist  as  Weismann  considers  that 
natural  selection  can  be  proved  only  in- 
directly. He  says:  *'A  direct  estimation  of 
the  relative  protective  value  of  the  two 
colours  [of  a  Sphingid  caterpillar]  is  alto- 
gether out  of  the  question.  The  survival 
of  the  fittest  cannot  be  proved  in  nature, 
simply  because  we  are  not  in  a  position  to 
decide  a  priori  what  the  fittest  is."  As  Mr. 
E.  S.  Russell  remarks:  "This  is  a  significant 
admission  from  the  protagonist  of  pure 
Darwinism,  but  he  admits  too  much.  It  is 
true  we  cannot  decide  a  priori  what  the  fittest 
is,  but  we  can  discover  by  observation  and 
experiment  whether  or  no  protective  colour- 
ation has  selective  value.  A  case  in  point 
is  given  by  Mr.  A.  P.  di  Cesnola  in  a  short 
but  highly  interesting  paper  in  *Biometrika' 
for  1904. 

"It    is    well    known    that    the    'praying 


SELECTION  1G3 

Mantis,'  Mantis  religiosa,  occurs  in  Italy 
in  a  green  and  a  brown  form.  The  former  is 
usually  to  be  found  on  green  grass,  the  latter 
on  herbage  browned  by  the  sun.  Mr.  Cesnola 
tied  down  among  green  herbage  twenty  green 
Mantis,  and  among  withered  grass  a  similar 
number  of  brown  individuals.  After  seven- 
teen days  they  were  all  alive.  He  also 
tethered  twenty-five  green  Mantis  among 
brown  herbage,  and  they  were  all  dead  after 
eleven  days.  The  converse  experiment  was 
also  made,  forty-five  brown  Mantis  being 
exposed  on  green  grass,  and  of  these  only  ten 
survived  at  the  end  of  seventeen  days.  Most 
of  the  Mantis  were  killed  by  birds;  five  of  the 
green  ones  were  killed  by  ants.  Here,  then, 
is  a  proof,  quite  conclusive  though  the  num- 
bers are  small,  of  the  selective  value  of  the 
protective  colouration  of  both  races  of 
Mantis.  If  green  Mantis  and  brown  Mantis 
be  exposed  on  green  grass,  the  green  ones 
will  survive  rather  than  the  brown,  the 
death-rate  will  be  selective.  Such  a  simple 
experiment  gives  more  solid  support  to  the 
view  that  protective  colouration  is  due  to 
natural  selection  than  any  accumulation  of 
probabilities. " 

It  is  of  enormous  importance  that  cases 
similar  to  the  above  should  be  accumulated, 
so  that  stability  may  be  given  to  the  theory 


164  EVOLUTION 

of  natural  selection  by  actual  evidence  tliat 
the  survivors  survive  and  the  eliminated  are 
eliminated  because  of  some  differentiating 
peculiarity  or  peculiarities.  Hence  a  few 
more  examples  may  be  given. 

Poulton  fastened  600  pupse  of  the  tortoise- 
shell  butterfly  to  nettles,  tree-trunks,  fences, 
walls,  and  so  on.  At  Oxford,  the  mortality 
was  93  per  cent.,  and  the  only  pupse  that 
survived  were  on  nettles,  where  they  were 
least  conspicuous.  In  the  Isle  of  Wight,  the 
elimination  was  92  per  cent,  on  fences,  as 
against  57  per  cent,  among  nettles.  Here, 
again,  there  was  definite  evidence  of  dis- 
criminate elimination. 

Professor  Crampton's  very  careful  research 
on  the  pupae  of  a  Saturnid  moth,  proved  dis- 
criminate elimination,  and  yielded  also  this 
interesting  result,  that  the  selected  characters 
(for  the  most  part  concerned  with  dimensions 
and  proportions)  were  not  such  as  would  have 
appeared  to  be  directly  or  indirectly  "useful" 
to  their  possessors,  though  they  were  de- 
monstrated to  have  the  high  utility  of  deter- 
mining survival — which  is  indeed,  for  the 
evolutionist,  the  final  criterion  of  utility. 

Professor  Bumpus  took  136  benumbed 
house-sparrows  into  his  laboratory,  where 
72  revived  and  64  succumbed.  There  were 
general   differences — of   a   somewhat   subtle 


SELECTION  1G5 

sort — between  those  that  revived  and  tliose 
that  succumbed.  General  stability  of  struc- 
ture was  the  essential  characteristic  of  the 
former. 

The  fine  researches  by  which  the  late  Pro- 
fessor Weldon  proved  discriminate  elimina- 
tion in  shore-crabs,  and  by  which  Professor 
Karl  Pearson  proved  a  selective  death-rate 
in  man,  are  of  the  highest  importance,  but 
they  require  more  exposition  than  we  can 
give  here. 

We  may  round  off  this  section  with  two 
simple  observations  whose  picturesqueness 
may  emphasize  our  present  point. 

Professor  Davenport,  of  the  Carnegie  In- 
stitution for  Experimental  Evolution,  had 
300  chickens  in  a  field,  80  per  cent,  white 
or  black  and  conspicuous,  20  per  cent,  spot- 
ted and  inconspicuous.  In  a  short  time 
twenty-four  were  killed  by  crows,  but  only 
one  of  the  killed  was  spotted. 

Finally,  a  kindred  and  recent  field  obser- 
vation of  our  own.  In  a  heavy  snowstorm 
at  Johannesburg  in  August  1909,  many 
hundreds  of  trees  were  destroyed  by  the 
weight  of  snow  on  the  branches.  It  was 
interesting,  after  the  storm,  to  notice  that 
the  elimination  was  in  a  marked  degree 
discriminate.  The  trees  that  suffered  most 
were  the  imported  Australian  trees,  such  as 


166  EVOLUTION 

the  Blue  Gums  and  Black  Wattles,  quickly 
growing,  with  soft  wood,  and  with  abundant 
foliage  that  caught  the  snow.  On  the  other 
hand,  the  deodars  from  the  Himalaya  moun- 
tains, constitutionally  adapted  to  let  the 
snow  slide  from  their  pendulous  branches 
and  acicular  leaves,  had  hardly  a  twig  broken. 

Implications  of  the  Concept  of  Nat- 
ural Selection. — As  a  naturalist  of  very 
rich  experience  Darwin  realized  the  complex- 
ity of  the  evolution  problem  more  than  most 
naturalists  have  done,  and  a  careful  study  of 
his  sentences  makes  it  quite  clear  that  when 
he  used  phrases  like  "struggle  for  existence" 
and  "natural  selection,"  which  have  acquired 
by  familiarity  a  somewhat  hard  and  mechani- 
cal sound  in  our  ears,  he  had  a  singularly  rich 
concrete  content  in  his  mind. 

"Nothing  is  easier,"  he  said,  "than  to 
admit  in  words  the  truth  of  the  universal 
struggle  for  life,  or  more  difficult — at  least 
I  have  found  it  so — than  constantly  to  bear 
this  conclusion  in  mind."  .  .  .  "I  use  this 
term  ['struggle  for  existence']  in  a  large  and 
metaphorical  sense,  including  dependence  of 
one  being  on  another,  and  including  (which 
is  more  important)  not  only  the  life  of  the 
individual,  but  success  in  leaving  progeny." 
.  .  .  "Nature  may  be  compared  to  a  surface 
on  which  rest  ten  thousand  sharp  wedges 


SELECTION  1G7 

touching  each  other,  and  driven  inward  by 
incessant  blows."  ...  "It  may  be  meta- 
phorically said  that  natural  selection  is 
daily  and  hourly  scrutinizing  throughout 
the  world  the  slightest  variations."  .  .  . 
"Battle  within  battle  must  be  continually 
recurring  with  varying  success;  and  yet  in 
the  long  run  the  forces  are  so  nicely  balanced 
that  the  merest  trifle  would  give  the  victory 
to  one  organic  being  over  another." 

What  we  wish  to  suggest  is,  that  Darwin's 
characteristic  fundamental  idea  of  the  in- 
tricacy of  interrelations  in  the  web  of  life, 
lies  below  the  idea  of  the  struggle  for  exist- 
ence, and  therefore  below  the  idea  of  natural 
selection.  Unless  we  appreciate  the  funda- 
mental natural  history  fact  of  the  web  of  Hfe, 
we  cannot  rightly  understand  how  slight 
differences  can  be  of  critical  moment  in 
determining  survival.  The  entanglements 
are  so  intricate  that  a  slight  variation  may  be 
of  survival-value  to  its  possessor. 

There  is  another  consideration  which 
Darwin  had  certainly  in  mind,  and  which, 
like  that  just  explained,  has  often  been  lost 
sight  of  since.  It  is  illustrated,  for  instance, 
by  the  researches  of  Bumpus  and  of  Cramp- 
ton  on  the  survival  of  sparrows  and  pupaj 
respectively.  The  point  was,  that  the  sur- 
vivors  seemed   to   survive,   not  because  of 


168  EVOLUTION 

single  peculiarities,  but  because  of  their 
general  stability  and  efficiency.  As  we  have 
already  hinted,  we  must  still  admit  what 
Darwin  admitted  more  than  fifty  years  ago — 
that  it  is  extraordinarily  difficult  to  say 
precisely  why  one  species  has  been  victori- 
ous over  another  in  the  great  battle  for  life. 
Part  of  the  difficulty  is  to  be  found  in  the 
fact  that  there  is  seldom  a  simple  issue. 

As  Russell  puts  it: — 

"We  should  think  of  each  creature  as 
being,  as  it  were,  the  point  of  intersection  of 
a  number  of  selection  processes,  of  as  many 
processes  as  there  are  significant  characters; 
and  since  the  signfficance  of  characters  must 
change  with  the  development  and  growth  of 
the  organism  and  with  every  alteration  in 
its  environment,  so  the  sum  of  selection 
processes  to  which  the  organism  is  subjected 
must  be  an  ever-changing  one." 

"The  survival  or  non-survival  of  the 
organism  will  be  determined  by  the  resultant 
of  all  these  selection  processes,  and  though 
the  exact  manner  of  it  be  extremely  complex, 
it  will  be  the  most  generally  efficient  organ- 
ism which  will  on  the  average  survive.  Its 
characters  will  be  such  as  have  remained 
*  useful'  throughout  its  life,  such  as  have 
adapted  the  organism  to  the  generality  of 
life-conditions  under  which  it  has  lived." 


SELECTION  109 

Different  Kinds  of  Selection. — There 
are  two  main  modes  of  natural  selection. 
There  is  the  ordinary  "lethal  selection," 
which  works  by  the  discriminate  elimination 
of  the  relatively  less  fit;  and  there  is  "repro- 
ductive selection,"  which  works  through  the 
increased  and  more  effective  reproductivity 
incident  on  the  success  of  the  more  fit.  When 
Darwin  says  "natural  selection  acts  by  life 
and  death  ...  by  the  survival  of  the  fittest 
and  by  the  destruction  of  the  less  well-fitted 
individuals,"  he  describes  lethal  selection, 
and  many  use  the  term  natural  selection  in 
this  sense  only.  But  when  Weismann  says: 
"Those  that  are  best  adapted  in  colour 
will  secure  the  most  abundant  food  and  will 
reproduce  most  prolifically,  and  they  will 
thus  have  a  better  prospect  of  transmitting 
their  usual  colouring  to  their  offspring,"  he 
is  obviously  describing  reproductive  selec- 
tion. 

Karl  Pearson  draws  a  distinction  between 
"secular  selection,"  which  is  Darwin's  natu- 
ral selection,  and  "periodic  selection,"  which 
is  less  easily  detected.  The  difference  is 
this:  in  the  ordinary  process  of  natural 
selection  a  change  in  the  mean  value  of  the 
selected  character  must  be  effected  from  one 
generation  to  another.  But  it  might  also 
happen  that  the  extreme  deviations  from  the 


170  EVOLUTION 

mean — e.g.  the  giants  and  the  dwarfs — were 
cut  off,  while  the  mean  value  of  the  character, 
e.g.  the  average  stature,  remained  unchanged. 
This  is  "periodic  selection,"  whose  reality 
Weldon  proved  in  the  case  of  one  of  the  snails : 
it  can  be  detected  by  the  diminution  in  the 
extent  or  range  of  variability. 

There  are  other  extensions  of  the  selec- 
tion-idea. Thus  in  social  insects  like  ants, 
where  community  competes  with  community, 
we  see  an  adumbration  of  the  intersocietary 
struggle  and  selection  which  we  are  familiar 
with  in  mankind.  There  is  also  some  meas- 
ure of  "struggle  of  parts  within  the  organ- 
ism," as  Roux  called  it,  i.e.  between  compet- 
ing organs  and  tissues  and  cells;  and  where 
there  is  rapid  multiplication  of  elements  and 
discriminate  destruction  there  must  be  a 
definite  selective  process.  There  is  also  a 
well-known  struggle  between  potential  ova, 
clearly  illustrated  in  Hydra  and  Tubularia, 
reminding  us  of  the  struggle  between  sister 
queen-bees.  There  is  a  kind  of  struggle 
among  the  hundreds  of  spermatozoa  in  their 
race  towards  the  ovum.  Allowing  a  margin 
for  chance,  the  most  vigorous  and  sensitive 
spermatozoa  will  tend  to  succeed  and  this 
will  be  for  the  advantage  of  the  species.  We 
are  quaintly  reminded  of  the  race  between 
drones   to   overtake   the   queen-bee   in   her 


SELECTION  171 

nuptial  flight.  There  is  also  sexual  selec- 
tion and  germinal  selection,  which  may  he 
conveniently  considered  in  separate  sections. 

Sexual  Selection. — In  extension  of  his 
theory  of  natural  selection  Darwin  proposed 
a  theory  of  sexual  selection  to  account  for 
the  frequent  occurrence  of  markedly  con- 
trasted secondary  sex-characters,  familiar 
in  cases  like  peacock  and  peahen,  stag  and 
hind.  There  are  two  modes  of  this  sexual 
selection:  the  combats  between  rival  males 
and  the  preferential  mating  where  the  fe- 
male chooses  or  seems  to  choose. 

The  issue  is  clearer  in  the  case  of  the  com- 
bats of  males.  For  when  the  younger  or 
weaker  candidates  are  killed,  or  expelled 
from  the  herd,  or  left  unmated,  there  seems 
little  reason  to  doubt  the  discriminateness 
of  the  elimination. 

As  to  preferential  mating,  there  is  no  doubt 
that  the  males,  especially  among  birds,  some- 
times show  off  their  varied  attractions,  but, 
as  Wallace  has  consistently  maintained, 
there  is  very  little  convincing  evidence  that 
the  female  chooses  a  partner  out  of  a  number 
of  suitors.  Still  less  is  there  evidence  that 
she  chooses  because  of  any  particular  excel- 
lence in  colour  or  in  song  or  in  dance.  In 
some  cases,  however,  there  is  evidence  that 
certain  males  are  left  unmated,  and    that 


172  EVOLUTION 

these  are  inferior  in  attractiveness.  In  the 
mysterious  case  of  spiders,  the  fastidious 
female  sometimes  kills  a  suitor  who  does 
not  adequately  please  her;  as  well  as  after- 
wards, it  may  be,  the  one  who  does. 

Since  Darwin's  day  many  of  the  supposed 
cases  of  preferential  mating  have  broken  down 
rather  badly  under  criticism,  but  there  are 
still  many  facts  to  go  upon.  It  seems  clear 
that  the  suitors  are  sometimes  highly  excited, 
and  that  their  displays — often  more  reflex 
than  deliberate — impetuously  excite  the  fe- 
male and  overcome  her  coyness — a  character 
which,  as  Groos  points  out,  is  of  no  incon- 
siderable racial  value.  In  some  passages 
Darwin  seems  to  credit  the  female  with  a 
high  degree  of  "taste"  or  aesthetic  fastidious- 
ness; but  he  was  probably  on  safer  ground 
when  he  wrote,  "it  is  not  probable  that  she 
consciously  deliberates;  but  she  is  most 
excited  or  attracted  by  the  most  beautiful, 
or  melodious,  or  gallant  males."  We  do  not 
know  very  clearly  what  choosing  may  mean 
to  a  hen-bird;  but  even  when  she  seems  to 
choose  some  slight  improvement  in  colour  or 
song  or  dance,  the  probability  is  that  she  is 
simply  surrendering  herself  to  the  male  whose 
tout  ensemble  has  most  successfully  excited 
her  sexual  interest. 

Germinal    Selection. — In    1895    Weis- 


SELECTION  173 

mann  suggested  that  the  concepts  of  "  strug- 
gle" and  "selection"  might  be  usefully 
extended  to  the  individual  items  which  com- 
pose the  germ-plasm,  or,  what  comes  to  the 
same  thing,  the  inheritance.  If  we  suppose, 
as  there  are  many  reasons  for  supposing,  that 
the  physical  basis  of  inheritance  in  the  germ- 
cells  is  composed  of  a  multitude  of  repre- 
sentative vital  particles  which  are  able  to 
feed,  grow,  and  multiply,  then  it  is  con- 
ceivable that  fluctuations  in  the  nutritive 
supply  of  the  germ-cells,  and  inequalities 
in  the  vigour  and  assimilating  power  of  the 
hereditary  constituents,  may  result  in  an 
intra-germinal  struggle  and  selection. 

The  general  idea  is  a  familiar  one,  that 
nothing  succeeds  like  success;  and  vice 
versa.  A  strengthened  representative  item 
or  determinant  in  the  germ-plasm  will  nour- 
ish itself  more  abundantly  than  its  neigh- 
bours. "It  may  get  into  a  permanent  up- 
ward movement,  and  attain  a  degree  from 
which  there  is  no  falling  back."  On  the 
other  hand,  a  weakened  determinant  will 
have  less  power  of  attracting  nutriment,  and 
will  tend  to  go  downhill.  If  it  be  the  deter- 
minant of  something  useful,  then  the  ordinary 
process  of  natural  selection  will  eliminate 
the  individual  that  develops  from  the  im- 
poverished germ-cell;    if  it  be  the   determi- 


174  EVOLUTION 

nant  of  something  useless  natural  selection 
will  not  interfere,  and  the  determinant  will 
continue   getting   weaker   every   generation. 

The  theory  of  germinal  selection  is,  of 
course,  an  hypothesis,  dealing  like  Mendel's 
theory  of  gametic  segregation  with  the  in- 
visible, but  it  may  be  nevertheless  useful 
in  enabling  us  provisionally  to  formulate  a 
number  of  very  puzzling  facts,  and  in  sug- 
gesting experimental  work,  on  which,  even- 
tually, we  must  base  our  conclusions  as  to 
these  abstruse  questions. 

According  to  Weismann,  germinal  selection 
helps  us  to  understand  the  dwindling  away 
of  organs  which  have  sunk  below  the  level 
touched  by  ordinary  natural  selection;  the 
occasional  exaggeration  of  organs  beyond  the 
limits  of  demonstrable  utility,  as  may  be 
illustrated  in  artificial  conditions  by  the  six 
feet  long  tail-feathers  of  some  Japanese 
cocks;  the  occurrence  of  definitely  directed, 
appropriate,  and  simultaneous  variations, 
and  much  more  besides.  It  plays  into  the 
hands  of  personal  selection;  or,  as  Weismann 
more  elegantly  phrases  it,  "it  supplies  the 
stones  out  of  which  personal  selection  builds 
her  temples  and  palaces:   adaptations'' 

Family  and  Group  Selections. — Though 
Darwin  did  not  wholly  overlook  this  (indeed 
in  at  least  one  notable  passage  he  expresses 


SELECTION  175 

it)  there  is  no  doubt  that  the  general  tone 
and  treatment  of  Darwinism,  even  hitherto, 
has  been  deeply  coloured  by  the  acute  indi- 
vidualism of  Darwin's  and  the  preceding  age. 
We  may  therefore  restate  here  the  concluding 
thesis  of  our  own  "Evolution  of  Sex"  (1889), 
since  elaborated  in  various  ways  by  Drum- 
mond,  by  Kropotkin  and  others.  It  is  that 
the  general  progress  both  of  the  plant  and 
the  animal  world,  and  notably  the  great  up- 
lifts (see  Chapter  III  above),  must  be  viewed 
not  simply  as  individual  but  very  largely  in 
terms  of  sex  and  parenthood,  of  family  and 
association;  and  hence  of  gregarious  flocks 
and  herds,  of  co-operative  packs,  of  evolving 
tribes,  and  thus  ultimately  of  civilized  socie- 
ties — above  all,  therefore,  of  the  city.  Hux- 
ley's tragic  vision  of  "nature  as  a  gladiatorial 
show,"  and  consequently  of  ethical  life  and 
progress  as  merely  superposed  by  man,  as 
therefore  an  interference  with  the  normal 
order  of  Nature,  is  still  far  too  dominant 
among  us.  It  threatens  even  to-day  to  con- 
fuse the  nascent  science,  and  still  more  to 
wreck  the  incipient  art,  of  Eugenics,  in  fact 
to  encourage  and  defend  that  massacre  of 
the  innocents  which  is  expressed  in  the  death- 
rate  of  every  community;  and  to  extend  this 
to  a  corresponding  view  of  legislation  and 
government.     Here,  in  fact,  is  opening  the 


176  EVOLUTION 

greatest  practical  controversy  of  our  science, 
in  comparison  to  which  all  others  have  been 
but  academic — that  ultimately  between  the 
Herodian  and  the  Magian  view  and  treat- 
ment of  the  child,  and  between  essential 
renewals  of  the  Csesarist  and  of  the  Christian 
ideals  of  the  community,  upon  our  modern 
spiral.  Yet  since  this  is  a  modern  spiral,  we 
must  harmonize  this  controversy;  we  must 
seek  the  due  correlation  of  the  ideals  of 
organic  and  of  psychic  selection.  For  this 
we  need  above  all  some  clearer  vision  of  the 
ideals  of  evolution — Olympian  for  the  body, 
Parnassian  for  the  spirit,  and  even  more — 
in  fact,  an  evolutionist  hope  and  aim  not 
only  for  the  life  of  the  individual,  but  in- 
creasingly for  the  uplift  of  the  race  and  of  the 
community.  On  the  way  towards  this, 
selective  consciousness  and  conscience  are 
indispensable,  love  as  individual,  love  as 
social;  and  with  these  sacrifice  also,  it  may 
be  of  love  or  of  parenthood  itself.  Nor  is  the 
social  control  a  mere  choice  between  Dra- 
conian harshness  on  one  hand  and  shallow 
philanthropy  on  the  other;  for  these  are  but 
rival  cruelties,  that  to  the  individual,  this  to 
the  race.  To  determine,  then,  the  ideal  goal 
and  the  true  process  of  selection  for  our  own 
species,  is  thus  the  supreme  problem  and  task 
which  are  opening  before  us  as  evolutionists. 


SELECTION  177 

Auxiliary  Hypothesis  of  Isolation. — 
We  have  already  referred  to  the  occurrence 
of  particular  species  on  particular  islands  in 
the  Galapagos  Archipelago,  and  there  are  a 
great  many  similar  cases  which  suggest  that 
isolation  means  something  in  evolution. 
The  red  grouse  is  peculiar  to  Scotland,  but 
it  has  doubtless  been  derived  from  the 
'^^/closely-related  stock  of  the  Scandinavian 
willow  grouse.  While  the  zoologist  has  lately 
distinguished  an  Orkney  vole  and  a  St.  Kilda 
wren,  every  one  knows  the  Shetland  pony, 
the  Highland  cattle.  There  are  said  to  be 
eighty  species  of  the  land-snail  Cerion  in  the 
Bahamas,  and  Gulick  records  over  200 
species  of  the  land-snail  Achatinella  in  the 
various  valleys  of  the  Sandwich  Island  Oahu. 

Many  evolutionists — Wagner,  Weismann, 
Gulick,  Romanes,  Jordan,  and  others — have 
worked  at  the  idea  of  Isolation,  as  a  directive 
factor  in  evolution;  and  Romanes  maintained 
that  it  was  a  sine  qua  non  in  the  origin  of  new 
species.  The  term  must  not  be  thought  of 
in  any  narrow  sense;  it  includes  all  the  means 
which  restrict  the  range  of  intercrossing 
within  a  species:  geographical  barriers,  such 
as  arise  when  a  peninsula  becomes  an  island; 
temporal  barriers,  such  as  arise  when  the 
members  of  a  species  reach  sexual  maturity 
at  different  times  of  year;  hahitudinal  bar- 


178  EVOLUTION 

riers,  when  a  species  splits  into  two  or  more 
castes  with  different  habits  of  Hfe;  physio- 
logical  barriers,  such  as  arise  by  some  va- 
riation in  the  reproductive  organs;  and 
psychological  barriers,  which  rest  on  profound 
antipathies. 

What  probably  happens  is  this :  a  success- 
fully vigorous  and  adaptive  species  spreads; 
the  several  contingents  become  isolated 
from  one  another;  and,  if  different  variations 
spring  up  in  several  or  all  of  the  contingents, 
then,  other  things  being  equal,  isolation 
will  favour  the  origin  of  distinct  species.  "I 
do  not  doubt,"  Darwin  said,  "that  isolation 
is  of  considerable  importance  in  the  forma- 
tion of  new  species."  It  may  be  of  some 
importance  in  preventing  intercrossing,  but 
it  is  much  more  likely  that  it  works  by 
bringing  about  close  inbreeding,  which  de- 
velops prepotency  or  stability  of  type. 

In  the  human  world,  the  manifold  range 
of  individuality  presented  by  regions  favour- 
able to  family,  village,  and  clan  isolations, 
such  as  Scotland  or  Norway,  Greece  or  Pales- 
tine, thus  becomes  intelligible.  Again,  in 
that  deterioration  of  the  cities  of  the  plain, 
which  is  so  frequent  throughout  history,  so 
evident  to-day,  we  may  increasingly  fear  an 
organic  factor  underlying  the  obvious  social 
ones — that  of  reversion   through  intercross- 


SELECTION  179 

Ing;  as  when  the  highly  individualized  races 
of  pigeon  sink  back  to  the  comparative 
uniformity  of  the  ancestral  rock-dove.  Yet 
from  this  apparent  regression,  really  a  pro- 
found and  intimate  panmixis,  a  thorough- 
going cross-fertilization,  who  shall  say  what 
new  variations  may  arise,  what  new  selections 
also — even  what  evolving  guidance  of  these? 
Eugenics  as  a  Renewal  of  Evolution. 
— Thus  we  return  to  man  as  transformist,  a 
discussion  already  opened  in  Chapter  II, 
but  this  time  appearing  in  a  fresh  perspec- 
tive. It  is  admitted  by  all  inquirers  into 
the  origins  of  civilization  on  one  hand,  into 
the  origins  of  cultivated  plants  and  of 
domesticated  animals  on  the  other,  that 
practically  all  these  familiar  and  indispen- 
sable companions  of  man  are  of  prehistoric 
origin,  and  have  risen  along  with  him,  as  he 
with  them.  But  now  the  corollary  of  this: 
imagine  the  immensity  not  only  of  patient 
labour,  but  of  selective  skill,  which  are  com- 
prised within  the  steps  from  wild  grasses  to 
cereals,  from  crab-apple  and  wild  olive  to  the 
vast  and  fruitful  groves  which  must  assur- 
edly have  covered  the  prehistoric  cultivation 
terraces  of  old,  stretching  as  these  did 
throughout  the  Mediterranean  region  from 
Portugal  to  Syria — thence  through  Asia 
Minor  to  Persia,  to  Korea  itself.     One  has 


180  EVOLUTION 

taken  tlie  pains  to  calculate  the  actual 
capital  value  of  these  ancient  Mediterranean 
terraces,  and  brings  out  the  marvellous,  yet 
credible,  result  that  the  actual  economic 
wealth  of  this  remote  prehistoric  world  far 
exceeded  that  of  the  Mediterranean  to-day; 
and  this  not  merely  in  its  agriculture,  or 
with  roads  and  railways  thrown  in,  but  with 
the  existing  cities  as  well!  Here  then  is  a 
view  of  the  early  human  past  very  different 
from  the  picture  of  groping  brutishness,  of 
promiscuity  and  struggle  with  which  nine- 
teenth-century anthropology  was  too  much 
obsessed;  for  if  we  seek  the  modern  repre- 
sentatives of  these  old  cultivators  and 
selectors,  these  breeders  and  arboriculturists, 
at  their  best  we  must  seek  them  at  the  very 
highest  growing-point  of  our  own  civilization 
to-day.  For  with  all  respect  to  the  great 
mechanical  inventors,  and  the  masters  of  the 
physical  sciences  who  have  accompanied 
them,  we  claim  a  higher  primacy  in  science 
for  Darwin  and  his  peers,  and  this  alike  as 
regards  vision  of  the  universe,  as  in  organic 
not  merely  physical  evolution,  and  in  poten- 
tial and  forthcoming,  if  not  yet  fully  actual 
contribution  to  the  service  and  uplift  of  man. 
In  short,  these  prehistoric  transformists  of 
wild  life  into  cultivated  fruitfulness  and 
domesticated  use,  had  already  among  them 


SELECTION  181 

their  Darwins  and  Vilmorlns,  their  Gartons 
and  Burbanks;  with  the  one  important 
difference — that  these  achieved  immeasur- 
ably greater  practical  results  than  have  as 
yet  their  modern  successors. 

Again,  is  it  likely  that  those  who  could 
transform  the  lurking,  wolfish  depredator 
into  the  trusty  guardian  of  their  flocks,  the 
wild  cattle  into  patient  ox  and  gentle  cow, 
the  wild  horse  into  the  Arab,  neglected  their 
own  breeding  as  we  and  our  progenitors 
have  done — or  even  misunderstood  it  as  all 
historic  aristocracies  have  done?  True,  we 
have  not  their  history  in  the  letter,  yet  we 
have  much  of  it  in  the  spirit;  that  of  the 
folk-tales  and  fairy  tales,  of  which  the  most 
childlike  and  sympathetic  of  the  sciences  is 
steadily  recovering  the  values  and  the  mean- 
ings; and  these  old  child-tales  are  even  re- 
turning towards  their  social  and  vital  appli- 
cations— above  all  that  of  presenting  the 
ideal  of  love  as  the  quest  of  life  which  our 
fathers  called  romantic,  which  we  now  call 
eugenic  and  think  modern.  Whereas  out  of 
all  this  recovery  of  the  golden  age  and  of  the 
ancient  garden  of  fruitful  labour,  does  there 
not  emerge  the  idea  that  its  guardians,  so 
much  wiser  and  happier  than  we  knew,  had 
thought  not  only  for  the  simpler  creatures 
they  cared  for  and  ruled  and  elevated,  but 


182  EVOLUTION 

for  themselves  and  for  each  other? — in  short, 
that  our  modern  Eugenics,  latest-born  even 
among  the  evolutionary  sciences,  may  yet 
be  among  the  very  oldest;  and  that  now 
once  more,  at  the  opening  of  that  new  epoch 
of  world-consciousness  and  world-activity 
which  is  involved  no  less  thoroughly  by  the 
evolution  theory  than  was  the  passing  in- 
dustrial age  by  the  advance  of  mechanical 
science,  the  ancient  evolutionary  past  is 
being  again  reborn? 


CHAPTER  VI 

ORGANISM,    FUNCTION    AND    ENVIRONMENT: 
IN  RELATION   TO   EVOLUTION 

The  Conception  of  Life — The  Evolution  Idea,  its  History 
— Theories  of  Evolution,  Classified — Relations  between 
Organism  and  Environment — Indirect  Importance  of 
Modifications — The  Role  of  Function — The  Living  Organ- 
ism— Theories  of  Vitalism — Initiation  into  Psychology. 

The  Conception  of  Life. — The  definition 
of  life  is  the  last,  not  the  first,  question  for 
the  student  of  Biology.  What  we  have  to 
do  first  is  to  study  the  actual  happenings,  the 
changes,  the  movements,  the  activities  that 
go  on  under  our  eyes.  It  is  only  after  we 
have  given  careful  study  to  the  actual  fact 
of  living — which  is  a  process,  a  dynamic 
relation — that  we  can  profitably  inquire  into 
the  particular  secret  of  the  agent. 

By  many  who  have  begun  at  the  wrong 
end — wrong  from  the  point  of  view  of 
scientific  method — the  conception  of  Life,  the 
organism's  secret,  has  to  be  left  as  a  mys- 
tery, or  is  mistaken  as  an  entity.  By  others 
it  is  thought  of  in  terms  of  chemical  sub- 
stance, like  the  "elixir"  or  "quintessence" 
of  old,  or  again  in  terms  of  modes  of  energy, 

183 


184  EVOLUTION 

which  are  "physical"  or  "vital,"  to  different 
schools,  of  materialistic  or  idealistic  leanings 
respectively,  albeit  physical  rather  than 
biological  in  either  case.  Our  present  point 
is  that  before  inquiring  into  the  secret  of  the 
organism — "Life"  in  the  innermost  and 
organismal  sense — we  must  seek  a  deeper 
appreciation  of  the  process  of  living.  What 
then  is  this.^^  On  the  one  hand  there  is 
the  Environment  in  its  action  upon  the 
organism;  and  on  the  other  the  Organism  in 
its  reaction  to  and  action  upon  the  environ- 
ment; the  dynamic  relation,  in  its  twofold 
aspect,  is  called  Function. 

The  Evolution  Idea:  its  History. — 
Before  v/e  seek  to  relate  the  various  theories 
of  evolution  factors  that  have  been  suggested 
to  the  three  categories  of  Biology — Organism, 
Function,  Environment — it  may  conduce  to 
clearness  to  consider  for  a  little  the  general 
"doctrine  of  descent." 

While  it  is  true,  as  Professor  Osborn  puts 
it,  that  "Before  and  after  Darwin"  will  al- 
ways be  the  "Ante  et  post  urbem  conditam" 
of  biological  history,  it  is  also  true  that  the 
general  idea  of  organic  evolution  is  very 
ancient.  Several  of  the  Greek  philosophers 
looked  upon  Nature  as  having  developed, 
and  as  being  still  in  process  of  change.  Aris- 
totle seems  to  have  recognized  an  ascending 


FUNCTION  AND  ENVIRONMENT    185 

series  from  polyp  to  man  and  an  age-long 
movement  towards  increased  perfection. 
Static  conceptions,  however,  prevailed,  with 
some  rare  exceptions,  through  the  long 
interval  between  Aristotle  and  Bacon,  who 
was  one  of  the  first  to  think  definitely  about 
the  mutability  of  species.  But  after  the 
Renaissance  it  was  among  the  "philos- 
ophers," not  among  naturalists,  that  the 
evolution  idea  began  again  to  live  and  move. 
The  first  naturalist  to  give  a  broad  and  con- 
crete expression  to  the  evolutionist  doctrine 
of  descent  was  Buff  on  (1707-1788) .  Erasmus 
Darwin  (1731-1802),  Charles  Darwin's 
grandfather,  was  another  firm  evolutionist, 
probably  influenced  by  Buff  on,  and  it  is  very 
interesting  to  observe  how  much  of  the 
argument  in  his  "Zoonomia"  might  stand 
to-day.  Lamarck  (1744-1829)  was  above 
all  thoroughgoing  in  his  evolutionism;  and 
Haeckel  rightly  speaks  of  his  "Philosophic 
Zoologique"  as  "the  first  connected  and 
thoroughly  logical  exposition  of  the  theory  of 
descent. " 

Besides  the  three  old  masters,  as  we  may 
call  them,  Buffon,  Erasmus  Darwin  and 
Lamarck,  there  came  other  quite  convinced 
pre-Darwinian  evolutionists  —  Treviranus, 
Etienne  Geoffroy  Saint-Hilaire,  Goethe, 
Robert  Chambers,  and  many  others.     Dar- 


186  EVOLUTION 

win  refers  to  thirty-four  more  or  less  evolu- 
tionist authors  in  his  Historical  Sketch,  and 
the  list  might  be  added  to.  Especially 
when  we  come  near  1858  do  the  numbers 
increase,  and  we  must  never  forget  that 
Herbert  Spencer  not  only  marshalled  the 
arguments  for  Evolution  in  a  very  forcible 
way  in  1852,  but  applied  the  formula  in 
detail  in  his  "Principles  of  Psychology"  in 
1855.  We  must  also  remember  that  the 
genetic  view  of  nature  was  insinuating  itself 
in  regard  to  other  than  biological  orders  of 
facts,  here  a  little  and  there  a  little,  and  that 
the  scientific  temper  had  ripened  consider- 
ably since  the  days  when  Cuvier  laughed 
Lamarck  out  of  court. 

We  have  inserted  this  historical  reference 
to  pre-Darwinian  evolutionists,  since  it  is 
important  to  shake  ourselves  free  from  all 
creationist  appreciations  of  Darwin;  but  it 
would  be  a  perversion  of  history  to  suggest 
that  he  simply  entered  into  the  labours  of 
his  predecessors.  In  point  of  fact,  he  knew 
very  little  about  them  till  after  he  had  been 
for  years  at  work.  Let  us  ask  rather  how 
it  was  that  Darwin  succeeded  in  winning 
a  world-wide  acceptance  of  the  evolution 
idea,  where  so  many  others  had  failed! 

Because,  in  the  first  place,  he  had  clear 
visions — "pensees  de  la  jeunesse,  executees 


FUNCTION  AND   ENVIRONMENT    187 

dans  I'age  rnur" — which  his  indocile  refusals 
to  submit  to  outworn  university  curricula 
had  made  possible,  which  the  "Beagle" 
voyage  made  fuller  and  more  vivid,  which 
an  unrivalled  British  doggedness  made  ever 
more  positive  and  real — visions  of  the  web 
of  life,  of  the  fountain  of  change  within  the 
organism,  of  the  struggle  for  existence  and 
its  winnowing,  and  of  the  spreading  genea- 
logical tree.  Because,  in  the  second  place, 
he  put  so  much  grit  into  the  substantiation 
of  his  visions,  putting  them  to  the  proof  in 
an  argument  which  is  of  its  kind — direct 
demonstration  being  out  of  the  question — 
quite  unequalled.  Because,  in  the  third 
place,  he  broke  down  the  opposition  which 
the  most  scientific  had  felt  to  the  seductive 
modal  formula  of  evolution,  by  bringing 
forward  a  more  workable  theory  of  the  pro- 
cess than  had  been  previously  stated.  Nor 
can  we  forget,  since  questions  of  this  magni- 
tude are  human  and  not  merely  academic, 
that  he  wrote,  in  his  mingled  simplicity 
and  condescension,  so  that  all  men  could 
understand. 

Theories  of  Evolution,  Classified. — 
So  far  the  general  doctrine  of  descent;  but 
some  of  the  pioneers  did  more  than  apply 
the  evolution  idea  as  a  modal  formula  of 
becoming:  they  began  to  inquire  into  the 


188  EVOLUTION 

factors  in  the  process.  How  are  their  the- 
ories related  to  the  three  categories —  Organ- 
ism, Function,  Environment? 

To  some  the  fundamental  fact  is  the  living 
Organism — a  creative  agent,  a  striving  will, 
a  changeful  Proteus,  selecting  its  environ- 
ment, adjusting  itself  to  it,  self-differentiating 
and  self-adaptive — Life  dominating  nature, 
master  of  its  fate. 

To  others  it  has  always  seemed  that  the 
emphasis  should  be  laid  on  Function — on 
activity  and  practice,  on  use  and  disuse,  on 
doing  and  not  doing. 

To  others,  again,  what  counts  for  most  is 
the  Environment.  This  wakes  the  organism 
to  action,  feeds  it  or  starves  it,  gives  it  new 
experiences  or  imprisons  it  within  the  old. 
Environment  prompts  the  organism  to  self- 
expression,  yet  moulds  it  and  prunes  it, 
punctuates  its  life,  and  finally  puts  in  the 
full  stop,  of  death. 

Let  us  take  some  historical  illustrations. 
There  is  no  doubt  that  Buffon  laid  great 
emphasis  on  Environmental  influences — es- 
pecially of  climate  and  food — as  direct  trans- 
forming factors. 

The  central  idea  of  Erasmus  Darwin's 
evolutionism  was  Functional:  that  wants 
stimulate  exertions  and  that  these  result  in 
improvements,  which  subsequent  generations 


FUNCTION  AND  ENVIRONMENT    189 

make  better  still.  This  was  Lamarckism 
before  Lamarck,  as  his  grandson  pointed  out. 

Lamarck  agreed  with  Buff  on  in  maintain- 
ing that  external  conditions  directly  moulded 
plants,  but  differed  from  him  in  denying  this 
for  animals,  "for  environment  can  effect  no 
direct  change  whatever  upon  the  organiza- 
tion of  animals."  In  so  doing,  despite  the 
obvious  exaggeration,  we  must  credit  him 
with  clear  recognition  of  the  relative  pas- 
sivity of  the  vegetative  life,  the  relative 
activity  of  that  of  the  animal.  The  central 
idea  of  his  theory,  however,  was  the  cumu- 
lative transmission  of  functional  modifica- 
tions: "Changes  in  environment  bring  about 
changes  in  the  habits  of  animals.  Changes 
in  their  wants  necessarily  bring  about  parallel 
changes  in  their  habits.  If  new  wants  be- 
come constant  or  very  lasting,  they  form  new 
habits,  the  new  habits  involve  the  use  of 
new  parts,  or  a  different  use  of  old  parts, 
which  results  finally  in  the  production  of  new 
organs  and  the  modification  of  old  ones." 
But  beyond  this  he  clearly  insisted  on  the 
inward  urge  or  effort  of  the  organism  to 
realize  its  inmost  wants,  and  to  express  this 
in  change  of  habits  and  even  of  structure. 

Treviranus  (1776-1837),  whom  Huxley 
ranked  beside  Lamarck,  was  on  the  whole 
like  Buff  on  in  attaching  chief  importance  to 


190  EVOLUTION 

the  influence  of  a  changeful  environment, 
both  in  modifying  and  in  eliminating.  But 
he  had  another  deep  idea,  which  Goethe 
shared,  of  an  inherent  formative  impulse  in 
the  creature.  "In  every  living  being  there 
exists  a  capability  of  an  endless  variety  of 
form-assumption;  each  possesses  the  power  to 
adapt  its  organization  to  the  changes  of  the 
outer  world,  and  it  is  this  power,  put  into 
action  by  the  change  of  the  universe,  that 
has  raised  the  simple  zoophytes  of  the  primi- 
tive world  to  continually  higher  stages  of 
organization,  and  has  introduced  a  count- 
less variety  of  species  into  animate  Nature." 

But  it  is  in  Goethe  that  we  find  the  fullest 
expression  of  the  idea  of  the  innate  tendency 
of  a  living  creature  to  fuller  self-realization. 
At  the  same  time  he  held  with  Lamarck  that 
"the  way  of  life  powerfully  reacts  upon  all 
form,"  and  with  Buffon  that  the  orderly 
growth  of  form  "yields  to  change  from  ex- 
ternally acting  causes." 

The  main  idea  of  Goethe,  of  an  inherent 
growth  force,  has  constantly  reappeared, 
notably  among  the  American  palaeontolo- 
gists: witness  Cope's  "bathmism";  and 
now  among  the  whole  rising  generation  of 
vitalists,  German  and  other.  The  anatomist 
and  systematist,  the  chemical  and  physical 
physiologist,  have  been,  and  still  are,  wont 


FUNCTION  AND  ENVIRONMENT    191 

to  reject  this;  and  not  without  reason — 
that  of  the  positivism  of  science,  which 
rightly  shrinks  from  the  acceptance  of 
abstract  entities  and  causes.  Undeniably, 
whatever  may  be  our  sympathy  for  these 
manifold  suggestions  of  vitalist  evolutionism, 
they  are  still  too  much  open  to  Moliere's 
ridicule,  as  of  explaining  the  effect  of  opium 
by  its  "dormitiveness." 

We  need  not  continue  these  historical 
illustrations,  but  the  important  point  is  this, 
that  some  naturalists,  such  as  Buffon,  em- 
phasized the  importance  of  the  Environ- 
ment; others,  such  as  Lamarck,  laid  the 
main  stress  on  Function;  others,  such  as 
Goethe,  discerned  that,  after  all,  the  mov- 
ing spirit  in  the  drama  of  evolution  is  the 
Organism.  It  may  be  said  without  dog- 
matism that  the  adequacy  of  an  evolution 
theory  is  in  proportion  to  its  recognition  of 
all  the  three  categories,  which  give,  in  point 
of  fact,  the  three  aspects  of  life. 

Surely,  whatever  may  be  the  limits  of 
Darwinism,  its  superiority  to  preceding 
evolution  theories  was  in  part  that  it  got 
nearer  to  seeing  life  whole.  The  Organism 
was  appreciated:  it  is  the  fountain  of  change; 
it  is  aggressive,  insurgent,  even  riotous,  in 
its  multiplication;  it  struggles,  it  even 
chooses.    Rightly  or  wrongly,  Function  was 


192  EVOLUTION 

also  appreciated:  use  and  disuse  have  their 
organic  consequences,  and  for  Darwin  these 
were,  at  least  in  part,  transmissible.  Simil- 
larly  the  Environment  was  appreciated,  alike 
in  moulding  and  in  pruning.  Finally  was 
added  the  idea  of  Nature's  environmental 
and  adaptive  sifting — the  essentially  new 
and  triumphant  doctrine  of  Natural  Selection. 

The  post-Darwinian  scepticism  as  to  the 
transmission  of  functional  and  environ- 
mental modifications  might  seem  to  involve 
a  denial  of  the  evolutionary  importance  of 
anything  but  the  varying  organism  and  the 
winnowing  environment;  but  what  it  really 
means  is  that  the  previous  appreciation  of 
the  evolutionary  importance  of  function  and 
of  environment  was  not  subtle  enough.  We 
ask,  therefore,  wherein  the  importance  of 
function  and  environment  may  consist,  if 
there  is  no  direct  transmission  of  the  indi- 
vidual modifications  which  they  undoubtedly 
produce.  This  involves  a  careful  inquiry 
into  the  relation  between  organism  and 
environment. 

Relations  between  Organism  and  En- 
vironment.— (1)  It  is  impossible  to  separate 
living  creatures  from  their  surroundings. 
To  do  so  in  fact  is  to  kill  them;  to  do  so  in 
theory  is  to  turn  biology  into  necrology,  a 
vice  which  has  always  too  largely  infested 


FUNCTION  AND  ENVIRONMENT     193 

our  science,  paralyzed  its  thinkers,  some- 
times even  skeletonized  or  mummified  them. 
There  is  an  endless  diversity  in  environments, 
and  some  of  them  are  most  extraordinary — 
the  iceberg,  the  hot  spring,  the  mountain  top, 
the  abysses  of  the  ocean,  the  cave,  the  in- 
terior of  another  creature — but  for  each 
kind  of  organism  there  is  an  indispensable 
minimum  of  supplies  and  influences,  apart 
from  which  it  cannot  develop,  or  grow,  or 
continue  to  live.  This  is  the  fundamental 
relation  of  living  things,  that  of  constant 
and   normal   environmental   dependence. 

(2)  But  surroundings  are  changeful  and 
the  living  creature  changes  with  them.  In 
many  cases,  where  the  external  changes  are 
regularly  recurrent,  like  seasons  and  tides, 
the  organism  falls  into  step  with  them;  so 
that  there  are  internal  rhythms,  punctuated 
by  external  periodicities.  The  latter  may 
come  to  be  needed  only  as  the  liberating 
stimuli,  or  trigger-pullers,  of  the  former. 
Experiments  show  that  some  young  tropical 
acacias  are  hereditarily  wound  up,  as  it 
were,  to  a  twelve  hours'  day  and  night — - 
times  of  leaf-expansion  and  leaf-closure. 
The  cold  of  winter  is  probably  the  stimulus 
rather  than  the  efficient  cause  of  the  brown 
stoat  becoming  the  white  ermine. 

(3)  To  some  of  the  irregular  changes  in  its 


194  EVOLUTION 

surroundings  the  living  creature  is  able  to 
adjust  itself  temporarily.  The  warm-blooded 
bird  or  mammal  can  within  limits  adjust  its 
heat-production  and  heat-loss  so  that  the 
temperature  of  the  body  remains  the  same 
whether  that  of  the  environment  rises  or 
falls.  In  the  case  of  many  of  these  transient 
adjustments  there  remains  no  abiding  result 
that  can  be  detected. 

(4)  Insensibly,  however — for  it  is  all  a 
matter  of  degree — we  pass  to  cases  where 
the  responses  to  environmental  change  last 
for  a  considerable  time.  Sun-burning  on  a 
summer  holiday,  increase  in  the  size  of  a 
muscle  after  a  course  of  exercises,  the 
blanching  of  the  banked-up  celery  are  familiar 
illustrations.  The  bodily  change  has  taken 
a  firmer  hold  than  in  the  case  of  transient 
adjustments,  but  it  is  still  a  passing  change. 
Like  a  bow  unstrung  the  organism  rebounds, 
approximately  to  its  previous  state. 

Semon  has  recently  propounded  a  theory 
— of  the  "Mneme" — which  is  of  interest  in 
this  connection.  The  general  idea  of  it  is, 
that  when  living  matter  is  affected  by  a 
stimulus,  its  quality  cannot  be  the  same  as 
it  was  before  the  stimulus.  Even  a  bar  of 
iron  is  not  quite  the  same  after  it  has  been 
once  struck;  how  much  more  a  living  crea- 
ture which  is  specialized  towards  gaining  and 


FUNCTION  AND  ENVIRONMENT    195 

garnering  experience.  There  is  always  some 
residual  effect;  this  Semon  calls  an  "en- 
gram,"  and  the  sum  of  the  engrams  of  a  liv- 
ing creature  is  its  "Mneme" — its  organic 
lore,  its  bodily  and  sub-conscious  memory 
we  may  practically  say. 

The  "Mneme"  may  have  particular  im- 
portance in  cases  where  penetrating  stimuli, 
like  those  of  the  seasons,  recur  periodically, 
re-vivifying  and  re-enforcing  the  previous 
accumulations  of  experience.  Along  this  line 
of  thought,  Semon,  and  following  him  Francis 
Darwin  and  others,  may  be  said  to  be  re- 
turning towards  a  position  again  essentially 
Lamarckian,  for  thus  the  results  of  experi- 
ence may  be  conceived  as  accumulating 
from  generation  to  generation,  even  al- 
though, as  Weismann  maintains,  individu- 
ally acquired  bodily  modifications  may  not 
be  entailed  as  such.  The  effects  of  an  often 
repeated  stimulus  may  saturate  through  the 
organism  by  nerve  paths  and  protoplasmic 
bridges  and  the  fluent  blood;  what  then 
precludes  them,  in  some  cases  at  least,  from 
reaching  even  the  germ-cells  in  their  recesses? 

In  this  connection,  it  is  only  just  to  recall 
the  remarkable  speculative  insight  of  the 
late  Samuel  Butler,  that  most  convinced  and 
argumentative  of  Lamarckians,  who,  more  or 
less  simultaneously  with  Hering  in  Prague, 


196  EVOLUTION 

propounded  a  generation  ago  much  the  same 
doctrine  of  "Organic  Memory,"  as  that 
which  we  now  owe  to  Semon.  Haeckel  too 
has  expounded  much  the  same  doctrine; 
and  no  doubt  in  increasingly  clarified  form  it 
must  henceforth  be  reckoned  with. 

(5)  Insensibly,  again — for  it  is  all  a  matter 
of  degree — we  pass  from  the  temporary  dints 
impressed  upon  the  organism  by  the  environ- 
ment to  those  that  last.  There  are  many 
cases  in  which  the  novel  conditions  provoke 
a  structural  change  from  which  there  can  be 
no  rebound,  the  limit  of  organic  elasticity 
having  been  passed.  These  lasting  changes 
are  technically  called  "modifications"  or 
"acquired  characters."  A  tree  may  be  per- 
manently blown  out  of  shape;  over-exertion 
at  high  altitude  may  strain  the  heart  beyond 
repair;  a  man  may  be  tanned  for  life  by  the 
tropical  sun. 

(6)  Quite  different  from  the  last  are  cases 
where  some  change  in  the  environment  of 
the  parent  provokes  a  variation  in  the  off- 
spring. The  best  instances,  as  yet,  are  to  be 
found  in  the  experiments  carried  on  for  many 
years  by  Tower  on  beetles  of  the  genus 
Leptinotarsa,  which  he  subjected  to  unusual 
conditions  of  temperature  and  humidity, 
when  the  male  and  female  reproductive 
organs  of  the  parent  were  at  a  certain  stage 


FUNCTION  AND  ENVIRONMENT    197 

in  their  development.  The  body  of  the 
parent  exhibited  no  modification,  but  the 
external  influence,  saturating  through  the 
body,  was  sometimes  operative  on  the  germ- 
cells  and  thus  on  the  offspring.  In  some 
cases  there  were  remarkable  changes  in 
colour  and  markings,  and  even  in  minute 
details  of  structure.  And  there  was  no 
reversion  to  the  parental  condition. 

(7)  Another  "organism-environment"  re- 
lation is  that  implied  in  the  struggle  for 
existence,  which  in  its  widest  and  truest 
sense  includes  all  the  reactions  of  living 
creatures  to  their  surroundings  and  diffi- 
culties. The  physical  world  is  careless  of 
life;  one  living  creature  presses  upon  an- 
other, competes  with  another,  devours  an- 
other. Thus,  while  the  environment  is  a 
stimulus,  it  is  also  a  sieve.  It  has  an  eliminat- 
ing action  which,  as  we  have  seen,  is  often 
discriminate;  it  sifts  and  winnows;  the 
result  is  extinction  for  some,  but  adaptation, 
and  this  it  may  be  a  degree  more  perfect, 
for  others. 

(8)  But  we  must  not  think  of  the  matter 
too  fatalistically,  as  if  organisms  were  always 
like  helpless  fishes,  around  which  the  environ- 
mental net  closed,  only  the  little  ones  getting 
through  the  meshes.  True,  they  cannot  by 
taking    thought    increase    or   decrease  their 


198  EVOLUTION 

stature,  even  to  save  tlieir  lives;  yet  they  are 
fertile  in  device,  persistent  in  endeavour. 
Even  the  worm  will  turn;  even  the  plant  will 
answer  back.  Living  creatures  are  agents; 
they  thrust  as  well  as  parry;  they  act  on 
their  surroundings,  modifying  them;  they 
are  ever  seeking  out  new  environments,  and 
conquering  them. 

The  foregoing  analysis  has  sufficiently 
shown  that  the  range  of  relations  between  the 
living  creature  and  its  surroundings  is  a  very 
complex  one, — of  functional  dependence,  of 
periodic  punctuation,  of  transient  adjust- 
ment, of  more  lasting  adjustment,  of  per- 
manent modification,  of  variational  stimulus, 
of  elimination  or  selection,  up  to  active 
initiative  upon  the  organism's  part.  The 
evolutionary  import  of  these  relations  is  no 
doubt  even  more  intricate  than  we  can  yet 
see.  The  old  theories  of  direct  adaptation 
in  response  to  altered  environmental  con- 
ditions, or  as  the  result  of  use  and  disuse, 
were  much  too  simple.  But  there  has  also 
been  far  too  great  simplicity  in  the  view 
too  long  prevalent  in  the  generation  after 
Darwin,  and  to  some  extent  even  to-day, 
that  each  species  must,  so  to  speak,  wait 
with  folded  hands,  until  fit  variations  emerge, 
whether  these  be  "spontaneous"  (i.  e.  un- 
explained), or  arise  in  com'se  of  shufflings  of 


FUNCTION  AND  ENVIRONMENT    199 

qualities  and  properties  that  undoubtedly 
must  occur  in  the  history  of  the  germ-cells. 

Indirect  Importance  of  Modifications. 
— The  interesting  suggestion  has  been  made, 
independently  by  Mark  Baldwin,  Lloyd 
Morgan,  and  Osborn,  that  useful  "modifica- 
tions" may  serve  as  the  fostering  nurses  of 
"variations"  in  the  same  direction.  We 
quote  from  Lloyd  Morgan  a  brief  statement 
of  this  idea:  "Suppose  that  a  group  of 
plastic  organisms  is  placed  under  new  con- 
ditions. Those  whose  innate  plasticity  is 
equal  to  the  occasion  are  modified  and  sur- 
vive. Those  whose  plasticity  is  not  equal 
to  the  occasion  are  eliminated.  .  .  .  Such 
modification  takes  place  generation  after 
generation,  but,  as  such,  is  not  inherited. 
.  .  ,  But  any  congenital  variations  similar 
in  direction  to  these  modifications  will  tend 
to  support  them,  and  to  favour  the  organism 
in  which  they  occur.  Thus  will  arise  a  con- 
genital predisposition  to  the  modifications 
in  question." 

"The  plasticity  still  continuing,  the  modi- 
fications become  yet  further  adaptive.  Thus 
plastic  modification  leads,  and  germinal 
variation  follows;  the  one  paves  the  way 
for  the  other." 

"The  modification,  as  such,  is  not  in- 
herited, but  is  the  condition  under  which 


200  EVOLUTION 

congenital  variations  are  favoured  and  given 
time  to  get  a  hold  on  the  organism,  and  are 
thus  enabled  by  degrees  to  reach  the  fully 
adaptive  level." 

Yet  another  consideration.  Although  we 
do  not  know  of  any  case  of  the  transmission 
of  a  modification  as  such,  or  even  in  a  repre- 
sentative degree,  we,  of  course,  agree  with 
Weismann  in  admitting  that  modifications 
may  have  secondary  effects  on  the  germ- 
cells,  and  thus  on  the  offspring.  In  this  way 
"nurture"  may  come  to  have  a  racial  im- 
portance. Nor  can  w^e  forget  that  the  en- 
vironment of  mammalian  mothers  is  bound 
to  have  an  influence  on  the  unborn  young, 
which  shares  the  maternal  life  so  closely. 
Apart  from  the  "mysterious  wireless  teleg- 
raphy of  antenatal  life,"  there  is  a  sharing 
of  the  diffusible  substances  carried  by  the 
blood. 

The  Role  of  Function. — We  cannot  go 
back  to  the  cruder  forms  of  the  Lamarckian 
theory,  and  believe  that  the  giraffe  length- 
ened its  neck  by  stretching  it;  yet  we  must 
beware  of  taking  too  simple  a  view  of  what 
function  implies.  What  are  the  certainties.^ 
We  know  that  development — the  expression 
of  an  inheritance — demands  functional  as 
well  as  environmental  stimuli.  Practice 
makes  an  organ  possible.    Without  exercise 


FUNCTION  AND  ENVIRONMENT    201 

it  will  not  develop  fully.  Again,  we  know 
that  changes  in  function  have  great  individ- 
ual importance.  By  force  of  smiting  one  be- 
comes a  smith.  Even  if  there  be  no  multi- 
plication of  muscle-fibres  after  the  more 
strenuous  function  began,  each  fibre  is 
larger  and  worth  more.  Contrariwise,  disuse 
means  deterioration;  when  we  rest  too  much 
we  rust.  No  one  has  ever  doubted  the 
individual  importance  of  functional  modi- 
fications. Further,  although  the  transmis- 
sion of  a  functional  modification  remains  un- 
proved, the  secondary  and  indirect  results 
may  influence  the  germ-cells  and  the  off- 
spring. It  is  idle  to  say  that  what  living 
creatures  do  or  fail  to  do  has  no  racial  im- 
portance. Another  certainty  is  that  by  its 
activity  a  living  creature,  being  no  mere 
puppet  of  fate,  may  alter  the  whole  situa- 
tion. This,  again,  may  have  evolutionary 
interest,  even  if  it  ends  fatally.  Admitting 
all  this,  can  we  say  more.f^ 

The  Living  Organism. — The  secret  of 
Life  is  baffling  to  the  human  intelligence, 
refusing  to  be  formulated.  Often  the  con- 
ception of  Life  has  seemed  to  biologists  to 
be  within  reach,  and  then  it  is  perhaps  far- 
thest away.  It  recedes  as  we  approach.  Yet, 
though  intelligence  fails,  do  we  not  at  times 
come  nearer  to  it  through  sympathy?   Words- 


202  EVOLUTION 

worth,  Emerson,  Meredith,  these  and  many 
other  Nature-poets  are  perhaps  the  truest, 
because  deepest,  biologists  of  us  all. 

It  is  partly  in  the  intrinsic  difficulty  of  the 
problem — vital  activity  being  something  be- 
tween mechanical  causality  and  our  conscious 
purposing — and  partly  in  the  way  that 
science  ever  takes  on  the  colour  of  its  time, 
that  we  must  look  for  an  explanation  of  the 
historical  oscillations  of  biology  between  the 
mechanistic  interpretations  of  the  living 
organism  and  the  vitalistic  appreciations  of 
it.  Now  it  is  a  machine  and  again  it  is  a 
spirit,  now  an  automaton  and  again  a  free 
agent,  now  an  engine  and  again  an  entelechy. 
The  pendulum  of  thought  continues  to 
swing. 

Despite  the  fact  that  as  yet  no  vitalist 
writer  has  succeeded  in  making  himself 
and  his  nomenclature  really  intelligible  to 
any  other,  and  that  the  frequent  gibes  at 
vitalistic  metaphysics  and  mysticism  remain 
largely  justified,  we  confess  that  the  modern 
movement  of  vitaHsm  has  our  increasing 
sympathy.  It  affects  our  evolutionism  to 
this  extent  at  least  that  we  feel  compelled  to 
recognize  the  persistence  of  some  originative 
impetus  within  the  organism,  which  expresses 
itself  in  variation  and  mutation,  and  in  all 
kinds  of  creative  effort  and  endeavour. 


FUNCTION  AND  ENVIRONMENT     203 

There  are  two  sides  to  all  doctrines  of  vital- 
ism— a  negative  side  which  argues  towards 
the  impossibility  of  holding  to  the  purely 
mechanistic  interpretation,  and  a  positive 
side  which  attempts  some  further  elucidation 
of  the  life-mystery. 

As  an  outspoken  statement  by  a  competent 
physiologist  and  physician  of  the  vitalist 
position,  on  its  critical  side,  we  may  take 
Dr.  Haldane's  recent  British  Association 
address  (Dublin,  1908).  "In  Physiology, 
and  Biology  generally,  we  are  dealing  with 
phenomena  which,  so  far  as  our  present 
knowledge  goes,  not  only  differ  in  com- 
plexity, but  differ  in  kind  from  physical  and 
chemical  phenomena;  and  the  fundamental 
working  hypothesis  of  Physiology  must  differ 
correspondingly  from  those  of  Physics  and 
Chemistry."  .  .  .  "The  physico-chemical 
theory  of  life  has  not  worked  in  the  past  and 
never  can  work.  As  soon  as  we  pass  beyond 
the  most  superficial  details  of  physiological 
activity  it  becomes  unsatisfactory;  and  it 
breaks  down  completely  when  applied  to 
fundamental  physiological  problems,  such  as 
that  of  reproduction." 

Theories  of  Vitalism. — A  constructive 
and  comprehensive  endeavour  to  formulate 
a  doctrine  of  vitalism  is  that  of  Dr.  Hans 
Driesch's  recent  Aberdeen  Gifford  Lectures, 


204  EVOLUTION 

in  which  the  author,  working  from  his  stand- 
point as  an  experimental  embryologist,  ad- 
vances technical  proofs  of  the  "autonomy 
of  life,"  and  of  its  specific  distinctiveness 
from  the  not-living.  He  advances  an  elabo- 
rate threefold  argument  to  show  how  the 
interpretation  of  a  living  creature  as  a 
machine  breaks  down,  both  in  regard  to  its 
functioning  and  its  development;  and  he 
seeks  to  show  that  it  is  necessary  to  postulate 
an  immaterial  autonomous  factor,  or  "en- 
telechy"  which  punctuates  the  transforma- 
tions of  energy  that  go  on  within  the  body. 
This  "entelechy"  is  the  living  creature's 
innermost  secret,  in  fact  its  directive  soul. 
Another  clear  and  comprehensive  exposi- 
tion of  a  theory  of  Vitalism  will  be  found  in 
Bergson's  "Creative  Evolution."  Bergson 
dwells  on  the  close  resemblance  between  the 
life  of  the  organism  and  our  own  personal 
experience.  We  change  without  ceasing;  the 
organism  is  in  a  state  of  ceaseless  flux  which 
we  call  metabolism.  Both  have  the  mysteri- 
ous quality  of  ''duree'' — but  duration  in  more 
than  the  merely  physical  and  chronological 
sense;  for  what  he  means  by  it  is  "the  con- 
tinuous progress  of  the  past  which  gnaws 
into  the  future  and  which  swells  as  it  advan- 
ces." "Our  personality  shoots,  grows  and 
ripens  without  ceasing.     Each  of  its  moments 


FUNCTION  AND   ENVIRONMENT    205 

is  sometliing  new  added  to  what  was  before. 
We  are  creating  ourselves  continually." 
So  of  an  organism  it  may  be  said  that  "its 
past,  in  its  entirety,  is  prolonged  into  its 
present,  and  abides  there,  actual  and  acting." 
"Continuity  of  change,  preservation  of  the 
past  in  the  present,  real  duration — the  living 
being  seems,  then,  to  share  these  attributes 
with  consciousness.  Can  we  go  farther  and 
say  that  life,  like  conscious  activity,  is  un- 
ceasing creation  .f^" 

Bergson  answers  this  question  by  an  em- 
phatic affirmative.  The  spontaneity  of  life 
is  manifested  by  a  continual  creation  of  new 
forms.  "A  hereditary  change  in  a  definite 
direction,  which  continues  to  accumulate 
and  add  to  itself  so  as  to  build  up  a  more 
and  more  complex  machine,  must  certainly 
be  related  to  some  sort  of  effort,  but  to  an 
effort  of  far  greater  depth  than  the  individual 
effort,  far  more  independent  of  circumstances, 
an  effort  common  to  most  representatives 
of  the  same  species,  inherent  in  the  germs 
they  bear  rather  than  in  their  substance 
alone,  an  effort  thereby  assured  of  being 
passed  on  to  their  descendants.  There  is  an 
original  creative  impetus  in  life,  which  passes 
from  generation  to  generation  of  germs,  is 
sustained  right  along  the  lines  of  evolution 
among   which   it   gets   divided,   and   is   the 


206  EVOLUTION 

fundamental  cause  of  variations,  or  at  least 
of  those  variations  that  count." 

We  see,  then,  how  Bergson  psychologizes 
life  without  needing  to  invoke  the  "spiritual 
influx" — too  much  a  "deus  ex  machina" — 
which  is  demanded  by  Wallace,  to  explain 
the  genesis  of  man's  higher  faculties,  and 
indeed  to  explain  the  other  great  steps 
in  evolution.  Metaphysical  and  abstract 
though  his  interpretation  remains,  too  shad- 
owy as  it  is  for  the  needs  of  the  working 
naturahst,  we  must  recognize  that  here  is  a 
fresh  and  forceful  re-statement  of  the  essen- 
tial thought  of  Lamarck,  of  Goethe,  of  Robert 
Chambers,  of  Butler,  and  of  later  vitalists; 
in  fact,  of  all  who  have  most  deeply  felt  the 
supreme  importance  of  the  organismal  fac- 
tor in  evolution.  More  even  than  this,  here 
is  a  new  conversion  of  the  philosopher  into 
the  biologist,  and  when  we  recall  the  enthu- 
siasm with  which  the  late  Prof.  William 
James  proclaimed  himself  as  the  disciple 
and  exponent  of  Bergson,  we  see  how  fruit- 
ful may  be  this  re-opening  alliance  of  the 
abstract  with  the  concrete  thinker.  Again, 
as  in  Spencer's  day,  our  biology  and  our 
psychology  have  to  be  correlated  and  unified 
anew,  and  all  towards  the  philosophy  of 
evolution.  Still,  with  all  respect  to  the  phi- 
losophers, who  have  taken  this  great  step 


FUNCTION  AND  ENVIRONMENT     207 

towards  becoming  naturalists,  we  cannot 
but  feel  that  the  next  step  in  progress  must 
depend  upon  how  far  we  naturalists  can  in 
our  turn  become  something  of  psychologists 
and  even  philosophers. 

It  is  a  matter  of  common  sense  and  expe- 
rience, which  we  are  all  verifying  any  and 
every  day  for  ourselves,  that  the  psycho- 
logically-minded person  can  and  does  see 
farther  into  life,  and  sees  more  aspects  of  it, 
than  the  most  skilled  mechanic,  be  he  the  in- 
ventor of  machines  or  the  discoverer  in 
physics.  After  all,  the  biologist  cannot  be 
content  until  he  becomes  something  more 
than  a  physicist  and  chemist,  an  anatomist, 
systematist  and  so  on:  beyond  its  struc- 
tures and  reactions,  life  has  an  aspect  of 
behaviour,  and  that  is,  after  all,  the  main 
one.  As  he  grasps  this,  he  becomes  a  bio- 
psychologist,  and  starts  upon  fresh  quests; 
at  first,  no  doubt,  and  properly,  armed  cap- 
a-pie  with  brass  instruments  and  copper 
wires.  Faithful  to  his  physico-mechanical 
upbringing,  he  measures  reaction-times,  he 
plots  curves,  he  again  reassures  himself  that 
there  is  nothing  more  in  Life.  But  one  day 
danger  and  opportunity  arouse  him;  another 
love  or  sorrow  awakens  him  altogether — not 
most  probably  to  any  mystic  vision  such  as 
vitalists  are  credited  with  by  their  opponents, 


203  EVOLUTION 

usually  far  too  generously,  we  suspect,  but 
at  any  rate  to  make  the  discovery  still  so 
rare  for  men  of  science,  albeit  an  open  secret 
to  plain  folk,  that  beyond  the  often  measur- 
able bio-psychoses  of  the  psychological  labo- 
ratory there  are  psycho-bioses,  often  im- 
measurable, in  the  greater  world-laboratory 
of  life.  After  this  initiation,  a  new  and 
before-unsuspected  thought- world  opens; 
and  within  this  begins  the  real  controversy, 
of  reconciling  the  claims  and  methods  of 
orderly  science  with  these  deepest,  yet  most 
incontestable,  data  of  experience.  In  such 
ways  the  enduring  contrast,  or  at  least  the 
bias,  of  the  mechanistic  and  the  vitalistic 
training  and  temperament  may  be  continued 
upon  a  higher  spiral,  with  results  ever  more 
fruitful,  yet  in  principle  already  in  view — 
from  one  side  that  of  carrying  physical  and 
chemical,  structural  and  functional  inquiries 
onwards  to  new  triumphs  of  analysis;  but 
also,  from  the  other  side,  that  of  tracing  the 
psychic  process  deeper  and  deeper,  into  the 
very  germs  and  origins  of  life.  In  a  word, 
then,  it  is  for  the  mechanistic  biologist  to 
cease  from  scoffing  at  the  vitalist  as  a  "mere 
mystic,"  and  to  set  about  mastering  psy- 
chology until  he  can  turn  scientific  clearness 
upon  his  vagueness.  Till  then  he  but  lays 
himself  open  to  a  counter-sneer  from  the 


FUNCTION  AND  ENVIRONMENT    209 

mystic,    and    a    worse    nickname — that    of 
"necrologist." 

Initiation  into  Psychology. — How  is  the 
biologist,  trained  in  the  dissecting-room,  the 
laborator}^  the  museum,  the  herbarium,  or 
even  in  the  garden  or  the  field,  to  get  at  the 
psychological  point  of  view,  even  when  he 
begins  to  feel  that  he  here  has  something 
to  learn,  that  he  in  fact  requires  it,  if  he  is 
to  be  a  biologist  indeed. ^^  Even  in  Bergson, 
much  more  in  the  German  vitalists,  there  is 
too  much  of  the  intangible.  Let  him  begin 
with  Darwin  himself,  and  he  may  soon  feel, 
that  like  many  an  admiring  disciple  before 
now,  he  has  not  grasped  the  fully  rounded 
thought  of  his  own  master.  With  rare 
exceptions,  like  Lloyd  Morgan  for  instance, 
what  naturalist  of  us  all  is  not  far  more  at 
home  with  Darwin  when  he  is  in  his  field 
watching  his  earthworms,  in  his  garden 
watching  the  bees,  in  his  greenhouse  among 
his  insectivorous  or  moving  plants,  or  in  his 
study  writing  "The  Origin  of  Species," 
than  when  already  as  a  youth  upon  the 
"Beagle,"  he  was  keenly  collecting  data 
which  eventually  formed  the  foundation  of 
his  "Expression  of  the  Emotions  in  Man 
and  Animals,"  a  masterwork  of  compara- 
tive psychology;  or,  as  a  grandfather  in  his 
easy-chair,  keenly  and  kindly  watching  the 


210  EVOLUTION 

daily  growth  of  his  child-playmate,  and  so 
laying  foundations  for  that  great  science  of 
mental  embryology  still  best  known  by  its 
fit  and  homely  name  of  child-study?  A 
naturalist,  too,  has  a  respect  for  embryology : 
let  him,  then,  take  as  guide  the  foremost 
of  American  mind-embryologists.  President 
Stanley  Hall  (see  the  American  Darwin  Cen- 
tennial volume,  "  Fifty  Years  of  Darwinism"), 
who  after  creating  a  very  paradise  for  the 
guild  of  brass  instruments,  and  long  and  lead- 
ing services  to  child-study,  has  of  later  years 
applied  himself  to  the  no  less  fruitful  and 
perhaps  even  more  important  field  of  Ado- 
lescence; that  magic  Dionysiac  moment  of 
human  metamorphosis,  in  which  wisdom  and 
folly,  madness  and  genius  strive  for  mastery, 
and  ferment  out  from  within  the  issues  of 
each  maturing  life,  in  passion  or  apathy, 
virtue  or  vice,  social  service  or  crime,  health 
or  insanity.  For  him  as  for  Darwin  "the 
soul  of  man  is  no  whit  less  the  offspring  of 
animals  than  is  his  body.  Our  psychic 
powers  are  new  dispensations  of  theirs.  The 
ascending  series  of  gradations  is  no  more 
broken  for  the  psyche  than  for  the  soma." 
Following  Darwin  still,  his  "method  is  always 
and  everywhere  objective  and  observational, 
never  subjective  or  introspective.  .  .  .  The 
true   ultimate  knowledge  of  our  psyche   is 


FUNCTION  AND  ENVIRONMENT    211 

the  description  of  all  developmental  stages 
from  the  amoeba  up;  and  those  move  most 
surely  among  the  altitudes  who  have  most 
carefully  explored  the  depths  in  which  the 
highest  human  powers  originate.  Emotions 
are  best  studied  in  their  outward  expressions 
of  gesture,  will  is  investigated  by  the  study 
of  behaviour,  intelligence  by  massed  in- 
stances of  sagacity,  and  not  by  analysis 
under  old  rubrics." 

With  example  like  this  of  Darwin's,  and 
guidance  like  this  of  Stanley  Hall's,  no 
biological  brother  need  fear  to  enter  the 
school  of  psychology,  as  we  ourselves  have 
done,  albeit  also  tardily.  From  its  many 
and  ever-widening  outlooks  new  views  ap- 
pear; on  one  side,  perhaps,  a  glimpse  of  how 
to  clear  up  the  vagueness  of  current  vitalism, 
and  in  any  case  many  ways  of  mellowing  the 
crudeness  of  current  mechanism. 


CHAPTER  VII 

EVOLUTION    THEORIES    IN    THEIR    SOCIAL 
ORIGINS  AND  INTERACTIONS 

Evolution  theories:  their  history  from  social  side — Limi- 
tations yet  advantages  of  social  outlooks — From  social 
progress  to  naturalist  outlook — Science  in  its  relation  to 
labour — Science  in  Philosophy,  Education  and  Life — The 
natural  sciences  once  more — Summary  of  preceding  argu- 
ment— Education  through  nature-occupations  to  vocations 
— Rustic  and  urban  as  contrasted  in  thought — Needed 
renewal  of  rustic  point  of  view. 

In  the  introduction  we  saw  that  the  doctrine 
of  evolution  was  on  one  side  a  generalization 
from  science  after  science — from  astronomy 
and  geology,  even  sooner  and  more  plainly 
than  from  zoology  and  botany;  from  phi- 
lology and  other  human  sciences  also.  We 
saw  the  faith  in  evolution  arising,  less  con- 
sciously, no  doubt,  but  perhaps  all  the  more 
deeply;  and  through  the  social  transfor- 
mations of  its  age.  The  generation  of  cul- 
minating political  revolution  in  France,  that 
of  the  culmination  of  the  industrial  revolu- 
tion in  England,  have  thus  expressed  them- 
selves through  Lamarck  and  Darwin  more 

212 


EVOLUTION  THEORIES  213 

clearly  than  either  thinliers  ever  dreamed, 
or  than  their  respective  exponents  and  dis- 
ciples have  realized. 

The  wealth  of  first-hand  observation  from 
which  Darwin  and  his  successors  generalized 
their  conviction  of  "the  all-sufficiency  of 
natural  selection"  was  thus  a  less  simple  and 
child-like  discovery  of  Nature  than  it  seemed; 
it  was  a  new  and  modern  selection  from  the 
wealth  of  Nature's  aspects  and  interests. 
For,  when  all  is  said  and  done,  "the  eye  sees 
only  what  it  brings  with  it  the  power  of 
seeing."  What  are  Lamarck's  interpreta- 
tions of  the  effects  of  use  and  disuse,  his 
assured  insistence  upon  the  interior  freedom 
of  the  organism  to  realize  its  inmost  capaci- 
ties, but  the  new  step  in  social  progress 
through  abandonment  of  outworn  orders  of 
society,  the  freedom  opening  before  new  ones? 
"La  carriere  ouverte  aux  talents"  is  pure 
Lamarckism;  so  again  the  splendid  over- 
assurance  of  the  Napoleonic  epic,  that  "every 
French  soldier  carries  a  marshal's  baton  in 
his  knapsack."  But  the  colder  business 
view  so  characteristic  of  English  thought 
came  to  prevail  over  such  political  and  mili- 
tary exaggerations;  the  ideals  of  mechanical 
efficiency  and  of  individual  and  financial  suc- 
cess rising  above  the  ruins  of  liberal  aspira- 
tions and  of  imperial  achievements  as  they 


214  EVOLUTION 

have  so  often  done.  Hence  a  view  of  evolu- 
tion essentially  mechanical,  in  terms  of  the 
division  of  labour,  the  cumulative  patenting 
and  the  like,  which  were  gradually  evolving 
the  express  locomotives  or  the  manufactur- 
ing plant  of  Darwin's  day,  and  now  the  fly- 
ing-machine in  our  own.  Hence,  too,  views 
essentially  competitive  and  commercial,  albeit 
of  various  shadings,  from  old-fashioned 
individual  efficiency  to  cheaper  and  cheaper 
undersellings,  with  advantages  here  from 
advertisements  more  and  more  brightly  and 
seductively  coloured,  there  from  deceptive 
imitations  more  and  more  subtly  wrought. 
"Competition  is  the  life  of  Trade":  then 
why  not  also  the  trade  of  Life?  Yet  with 
all  this  freshness  and  vigour  of  economic 
application,  there  has  prevailed  in  the  main, 
and  still  prevails,  a  naive  forgetfulness  of 
the  social  origins  of  these  naturalists'  dis- 
coveries. 

Similarly  in  neo-Darwinian  times.  With 
united  and  real  respect  for  Weismann,  for 
whose  work  one  of  us  has  once  and  again 
acted  as  translator  and  editor,  the  other  yet 
ventures  to  urge  one  of  the  very  few  criti- 
cisms which  that  wide  and  fair-minded  and 
subtle  thinker  seems  never  to  have  consid- 
ered :  the  striking  social  parallelism  of  his  ov/n 
theory   of  the  germ-plasm,   of   the  ovum's 


EVOLUTION  THEORIES  215 

strict  inheritance,  with  the  thought  of  con- 
temporary Germany;  with  the  victories  and 
hegemony  of  Prussia,  the  renewed  claims  of 
its  aristocracy  also;  and,  above  all,  with  its 
doctrine  of  race,  political  and  anthropolo- 
gical combined.  The  intermediate  step  be- 
tween this  ruling  Prussian  world  of  action 
and  Weismann's  ascendancy  in  speculative 
biology  is  indicated  by  the  widely  diffused 
doctrine  of  Count  Gobineau,  consciously  and 
avowedly  bio-social  as  this  has  been.  All 
these  movements  alike  have  now  found 
eloquent,  though  hardly  scientific,  expres- 
sion in  Houston  Stewart  Chamberlain,  whose 
contemporary  vogue  in  Germany  is  thus 
earned  and  explained. 

Limitations  yet  Advantages  of  Social 
Outlook. — But  the  reader  may  ere  now  be 
saying:  If  this  be  true,  if  biological  doctrines 
be  even  half  as  much  projections  of  their 
social  age  as  is  here  suggested,  what  becomes 
of  the  independent  scientific  value  they  have 
claimed,  and  which  we  are  asked  to  grant.? 
Is  your  science  merely  a  new  anthropomor- 
phism.?— and  if  so  how  does  it  differ  from  the 
mythological  accounts  of  Nature  it  claims 
to  displace.? 

The  answer  is  not  so  difficult  as  it  seems, 
the  result  not  so  unsatisfactory  after  all. 
The  independence  of  the  doctrines  of  any 


216  EVOLUTION 

science  from  the  social  life,  tlie  prevalent 
thought  of  the  generation  in  which  they  arise, 
is  indeed  a  fiction,  a  superstition  of  the 
scientist  which  we  would  fain  shatter  beyond 
repair;  but  the  science  itself  becomes  all  the 
sounder  for  recognizing  its  origins  and  its 
resources,  its  present  limitations  and  its 
needs  of  fresh  light  from  other  minds,  from 
different  social  moulds.  Robinson  Crusoe 
made  an  excellent  survey  of  his  island,  and 
felt  a  legitimate  scientific  assurance  of  its 
thoroughness,  a  corresponding  personal  pride 
also;  but  when  Friday  came,  bringing  with 
him  a  widely  different  tradition  of  culture,  his 
fresh  survey  not  only  enriched  his  master's 
at  many  a  point,  but  taught  him,  indeed 
each  of  them,  its  relativity  as  well.  Here 
indeed  is  the  practical  criterion  of  scientific 
conclusions,  their  verifiability  by  diverse 
minds.  So  far  then  from  sneering  at  La- 
marck as  an  impassioned  son  of  the  revolution, 
at  Darwin  as  a  shrewd  and  prosperous 
modern  Englishman,  at  Weismann  as  a 
German  ennobled,  and  so  on,  we  begin  to 
see  how,  just  as  "it  takes  all  kinds  of  people 
to  make  a  world,"  so  it  must  also  to  give 
anything  like  a  full  account  of  it,  to  clear 
these  partial  accounts  up  into  a  science. 
A  science  is  one  of  the  most  collective,  most 
historic,  of  products;  and  most  social  there- 


EVOLUTION  THEORIES  217 

fore,  though  the  custodians  of  its  heritage 
be  as  yet  few. 

There  is  a  time  for  everything,  and  since 
philosophy,  or  any  portion  of  it  worth  calHng 
generahzed  science  is  (or  at  least  should  be) 
the  ripened  fruit  of  experience,  the  retire- 
ment of  the  student  and  philosopher  from 
the  noise  and  turmoil,  the  delay,  hourly 
pressure  of  the  world,  is  as  necessary  and  as 
legitimate  a  process  as  is  setting  apart  the 
milkpan  to  let  the  cream  rise.  The  mistake 
arises  when  we  begin  to  think  of  this  isola- 
tion as  the  sole  essential,  and  overlook  that 
all  the  cream  we  get  comes  from  the  cow,  and 
from  such  pasture  as  we  can  give  her.  The 
qualities  and  defects  of  the  retiring  biological 
philosopher  thus  become  apparent.  Take 
Mr.  Spencer  for  choice.  After  an  education 
unusually  scientific,  an  experience  unusually 
practical,  including  participation  in  the 
greatest  constructive  activities  of  his  day, 
both  as  railway  engineer,  as  mechanical  in- 
ventor, and  in  its  theoretic  discussions  also, 
as  editor  and  as  economist,  he  takes  more  and 
more  general  views,  first  as  leader-writer, 
then  as  essayist,  and  thence  abstracts  him- 
self into  his  long  and  devoted  cloistered  life 
as  philosopher.  But  after  all,  how  little  in 
essential  thought  does  his  reasoned  philoso- 
phy get  beyond  its  initial  statement  in  his 


218  EVOLUTION 

sporadic  essays? — and  how  largely  are  these, 
in  qualities  and  in  limitations  alike,  the 
expressions  of  his  boyish  and  his  youthful 
education,  his  professional  experiences? 

From  Social  Progress  to  Naturalist 
Outlook. — Once  more,  then,  we  insist  upon 
the  progress  of  evolutionary  science  as  from 
social  progress  to  its  naturalist  application. 
In  our  opening  chapter  we  put  this  plainly 
enough,  but  as  it  were  once  for  all;  thence 
passing  as  naturalists  into  the  field,  and  as 
biologists  into  the  laboratory  and  study. 
Darwin  is  again  the  example  of  this  life- 
history  of  the  naturalist.  Malthus  once 
grasped  and  applied,  he  drew  no  more  drafts 
upon  political  economy,  consciously  at  least; 
and  his  many  disciples  and  continuators 
have  been  no  more  conscious  of  their  stoutly 
utilitarian  economics  than  was  M.  Jourdain 
of  his  prose:  though  of  course  it  has  been 
none  the  less  there  all  the  time.  Wallace, 
indeed,  practically  alone  among  Darwinians, 
and  more  divergent  and  original  than  his 
generous  loyalty  has  ever  allowed  him  to 
realize,  has  kept  in  touch  with  the  movement 
of  economic  thought,  and  that  in  later  and 
less  canonical  schools  especially;  he  has 
striven  to  throw  light  upon  other  puzzles 
and  controversies,  from  political  to  psycho- 
logical,  from  geographic   to   religious;    but 


EVOLUTION  THEORIES  219 

thereby,  despite  services  to  evolutionary 
biology  second  only  to  Darwin's  own,  he 
failed  to  widen  the  interests  of  fellow- workers 
henceforth  specialized,  and  perhaps  rather 
intensified  their  reluctance  to  venture  be- 
yond their  immediate  problems.  They  too 
were  doubtless  so  far  right  in  this:  their  re- 
examination of  Nature  in  the  light  of  the 
Darwinian  theory  has  been  a  great  task. 
But  now  on  many  sides  fresh  chapters  of 
evolutionary  study  are  opening,  and  there 
are  many  workers  who  feel  free,  even  con- 
strained, to  relate  and  unify  the  phenomena 
of  development  of  plants  and  animals  and 
man,  the  intricacies  of  structures  and  func- 
tions, variations  and  diseases,  amid  which 
have  lain  our  various  individual  trainings 
as  organic  evolutionists,  with  those  of  other 
evolutionists,  not  only  the  cosmic,  but  the 
social.  Hence,  then,  the  planning  of  this 
little  book — which  starting  with  the  social 
origins  of  biological  evolution  theories,  next 
naturally  gives  its  main  bulk  to  the  bio- 
logical theories  themselves,  but  increasingly 
suggests  the  fruitful  parallel  of  organic  and 
social  evolution;  and  now,  as  it  draws  to- 
wards conclusion,  it  argues  with  more  and 
more  insistence  for  the  conscious  renewal 
of  this,  as  a  working  partnership  hence- 
forward. 


220  EVOLUTION 

Science  in  its  Relations  to  Labour. — 
Note  here  another  difference  between  the 
opening  treatment  of  this  parallelism  and 
that  with  which  we  now  draw  to  a  close.  Bio- 
logical evolution  as  projection  of  a  social 
philosophy,  be  this  conscious  or  unconscious, 
and  the  resultant  renewal  of  Nature  studies 
as  observant  and  inductive  in  the  field,  are 
alike  the  expression  of  that  wisely  passive 
mood  in  which,  with  naturalist  as  with  poet, 
**we  see  into  the  life  of  things."  But  man 
^is  born  to  labour  also;  his  hands  have  made 
him  wise;  the  complex  brain  not  merely  or 
mainly  growing  up  in  vacuo  or  in  abstracto 
nor  even  in  encyclopaedia,  as  one  school  of  ed- 
ucationists after  another  has  falsely  thought 
and  wTongly  applied,  but  as  we  now  begin  to 
see  and  to  apply,  in  intimate  interaction  also 
with  the  skilful  and  strenuous  hand.  Science, 
no  less  than  fine  art,  is  essentially  of  the 
working  class.  Like  art  it  is  craft-experience, 
craft-skill,  craft-initiative,  for  the  scientist 
more  reflective,  as  for  the  artist  more  im- 
passioned. Science  is  always  observing,  in- 
quiring— blundering  therefore  also — with  the 
prentice;  is  in  fact  a  perpetual  apprentice; 
yet  skilled,  and  that  a  degree  beyond  the 
customary  journeyman — speculative,  ex- 
perimental, inventive,  with  the  best.  Fur- 
thermore,   Science   is   experienced,    critical. 


EVOLUTION  THEORIES  221 

comprehensive,  with  the  master,  and  hence 
of  such  service  to  his  large  undertakings. 
True,  the  working  world  around  us,  bound 
all  day  to  the  wheel  of  labour,  is  hypnotized 
more  even  than  is  the  middle  class  by  nominal 
wages  in  money  instead  of  real  wages  in  life; 
more  even  in  its  brief  leisure  than  the  upper 
class  by  fair  abstractions  and  fine  words; 
and  so  it  has  lost  sight  of  its  outstanding 
artist  leaders,  its  pioneering  scientist  ones, 
as  they  of  each  other.  Hence  as  yet  when 
new  leaders  emerge  amid  its  ranks  it  is  as 
amateur  barristers,  or  amateur  financiers, 
for  the  most  part.  Still,  the  reunion  of  arts 
and  sciences  with  labour  "is  comin'  yet  for 
a'  that,"  and  with  it  a  new  age  of  social 
evolution,  and  of  corresponding  impulse 
to  evolution  theory  also. 

Science  in  Philosophy,  Education,  and 
Life. — Of  this  incipient  renewal  of  philoso- 
phy with  social  life  the  discussion  of  prag- 
matism is  an  example;  but  for  our  purpose 
its  change  of  stress,  from  passive  knowledges 
to  active  purposes,  is  more  obviously  ex- 
pressed in  the  coming  in  of  manual  training 
to-day  after  that  of  scientific  instruction 
yesterday.  To-morrow  we  shall  realize  that 
more  of  free  and  creative  art  is  needed  to 
redeem  industry  from  its  mammonism  and 
its    drudgery,    as    science    from   formalism 


222  EVOLUTION 

and  cram;  thereafter,  with  the  unison  of 
all  three  will  come  education  indeed;  artistic, 
scientific  and  practical;  heart,  head,  and 
hand;  and  each  calling  out  the  others  to 
fuller  expression  and  development. 

Concretely,  how  can  this  dream  of  in- 
dividual development  so  important  for  the 
progress  of  science,  the  reading  of  evolution, 
be  actually  applied  and  brought  about?  So 
far  as  the  sciences  are  concerned — and  these 
are  commonly  esteemed  the  most  difficult— 
the  principles  of  its  apphcations  are  clear. 
While  the  services  of  each  science  to  practical 
life  are  constantly  insisted  on,  and  in  no 
danger  of  being  overlooked,  we  far  more 
often  and  readily  forget  the  rise  of  each 
science  from  practical  life.  But  the  historic 
beginnings  of  geometry  with  measurement 
are  again  in  progress  in  the  schools.  Those 
of  astronomy  with  navigation  have  long  been 
well  taught  to  the  sailor  youth,  and  now  the 
boy  scout  is  learning,  like  his  pastoral  an- 
cestors, to  find  his  time  by  the  sun,  his  way 
by  the  stars.  Nor  is  this  a  matter  of  ele- 
mentary education  merely;  here  lies  the 
main  progress  of  research  also,  that  higher 
education  of  the  individual  and  the  race 
together.  Thus  the  problems  of  daily  life, 
the  emergencies  of  practice,  called  out  the 
highest  powers  and  achievements,  from  Ar- 
chimedes of  old  to  Kelvin  yesterday. 


EVOLUTION  THEORIES  223 

For  fuller  illustration — whether  we  state 
on  principle  more  abstractly  (as  the  rise  of 
science  from  practice) — or  more  concretely 
(experimental  science  as  proletarian  expe- 
rience and  initiative),  we  cannot  do  better 
than  bring  to  these  tests  some  of  these  great 
leaders  of  science,  whom  the  uninitiated  still 
practically  think  of  as  magicians  and  wizards, 
much  as  they  did  of  their  predecessors  of 
old.  Take,  then,  Kelvin  and  Lister.  Leaving 
aside  the  too  common  London  populace 
view,  to  whom  these  names  are  impressive 
merely  as  Lords,  albeit  a  little  lower  than 
the  brewers;  or  the  more  educated  London 
view,  which  would  appreciate  them  as  suc- 
cessive Presidents  of  the  Royal  Society,  it 
is  plain  that  a  more  real  and  biographic 
understanding  of  the  one  is  as  the  farthest 
ranging  of  the  mathematical  and  the  ex- 
perimental physicists,  both  pure  and  ap- 
plied, and  of  the  other  as  the  renewer 
of  modern  surgery.  Biographically,  we 
understand  Kelvin  better  in  his  lifelong 
environment  of  Glasgow;  but  only  fully  as 
we  see  its  significance,  for  one  thing  as  the 
great  fiord  of  the  iron  shipbuilders,  with 
their  consequent  dangers  of  deranged  com- 
pass and  the  like,  whence  a  well-known 
example  of  Kelvin's  experimental  solutions. 
Here,  too,  arose  James  Watt,  with  his  Pro- 


224  EVOLUTION 

methean  control  of  new  energies;  and  here 
fitly  also  in  turn  Kelvin  to  control  the  yet 
subtler  and  more  potent  spark  of  electricity 
with  inventions,  each  a  literal  masterpiece 
of  craft  subtlety  and  of  manual  skill.  Kel- 
vin, whom  in  illustrious  old  age  the  world 
delighted  to  honour,  was  thus  as  truly  the 
master-smith  of  Glasgow  as  had  been  Watt 
before  him;  so  the  spacious  physical  labo- 
ratories of  every  university  in  the  world  to- 
day are  still  above  all  the  local  extensions  of 
William  Thomson's  cellar- workshop.  -^ 

So  Lord  Lister  is  not  to  be  understood 
primarily  even  as  surgeon-in-chief:  his  place 
in  history,  immortal  though  it  be,  is  also 
humble,  humbler  even  than  that  of  the 
plebeian  branch  of  the  profession,  the  bar- 
ber's. For  he  with  his  antiseptic  surgery 
is  "the  shepherd  with  his  tarbox  by  his  side"; 
more  simply  still,  since  full  shepherd-craft 
is  far  beyond  his  ken,  he  is  the  "tar-boy," 
who  waits  upon  the  shepherd,  ready  to  put 
on  his  dab  of  antiseptic  wherever  needed. 
So  Pasteur  was  not  essentially  a  magnate 
of  the  Legion  of  Honour,  the  member  of  two 
Academies  at  home,  and  of  all  abroad;  not 
even  primarily  the  great  chemist.  He  was 
a  tanner's  son,  born  and  bred,  that  is,  amid 
the  greatest  and  oldest  of  antiseptic  processes, 
and  developing  and  applying  it  all  his  life. 


EVOLUTION  THEORIES  225 

More  generally,  in  character  and  experience 
he  was  a  Jura  peasant,  with  all  the  French 
peasant's  tenacious  and  tireless  industry, 
his  manifold  minute  economies.  One  rare 
advantage  he  had,  and  this  it  was  which 
made  him  the  world's  master-peasant — the 
daintiest  ultra-feminine  eye  for  dirt,  and  as 
its  direct  and  woman-like  application  a 
super-housewifely  passion  for  cleaning.  How, 
out  of  these  simple  conditions,  these  homely 
and  humble  antecedents,  came  discoveries 
and  applications  revolutionizing  industries, 
agriculture,  medicine,  and  through  Lister 
surgery  (for  Lister  is  Pasteur's  tar-boy), 
we  have  tried  to  tell  elsewhere. 

So,  again,  the  botanist  is  in  the  university 
as  the  representative  of  the  old  herbalist,  the 
wise  woman  gathering  her  simples.  Lin- 
naeus, with  his  world-museum,  his  proudly 
entitled  "System  of  Nature,"  albeit  traveller 
and  scholar,  is  essentially  and  traditionally 
a  head-pharmacist,  the  most  orderly  on 
record  of  that  necessarily  tidiest  and  most 
careful  of  guilds.  Jussieu,  of  the  natural 
system  which  replaced  the  pharmacists' 
inevitably  more  artificial  one,  was  the  king's 
gardener,  the  man  of  living  flowers,  charged 
to  keep  the  queen  and  her  ladies  in  bouquets, 
and  so  getting  a  free  hand  to  vary  them,  and 
an    intelligent    and     questioning    audience 


226  EVOLUTION 

sometimes  to  explain  them  to,  whereby  in- 
deed botany  came  into  fashion.  Of  botany 
there  are  always  these  two  schools — the 
pharmacist's  and  the  gardener's;  so  its 
professors  belong  essentially  to  one  or  other, 
sometimes  partly  to  both,  but  never  thor- 
oughly: that  is  too  much  to  ask.  The 
zoologists  then?  These  are  hunters;  first 
out  after  big  game  with  its  dangers,  its 
trophies;  after  birds  too,  and  their  plumage. 
Sometimes  there  comes  to  one  the  vision  of 
St.  Hubert,  and  then  he  lays  aside  his  gun, 
and  takes  up  his  notebook  or  his  camera. 
Darwin  was  one  of  these  from  his  Beagle 
days  at  any  rate;  but  before  that,  he 
was  plainly  of  the  hunter  type — in  fact,  a 
born  truant,  the  stuff  true  poachers  are 
made  of. 

Other  naturalist-hunters  come  down  to 
smaller  and  smaller  deer,  next  to  their  fleas 
and  midges,  and  now  to-day  are  hunting  out 
the  parasites  within  these,  and  to  some  pur- 
pose. Other  naturalists,  again,  are  fisher- 
men, increasingly  expert,  their  huts  and  pools 
growing  into  zoological  stations,  their  nets 
searching  the  sea  from  its  surface-plankton 
to  abyssal  dredgings;  and  these  from  Arctic 
to  Antarctic.  Plainly  then,  the  natural 
sciences  grow  up  along  with  practical  life 
and  ever  learn  from  it  anew. 


EVOLUTION  THEORIES  227 

Summary  of  Preceding  Argument. — 
Collecting  now  all  the  threads  of  this  long 
discussion  towards  a  fuller  grasp  of  the 
studies  of  evolution,  the  result  is  plain 
enough.  Since  we  cannot  but  project  our 
human  thought,  our  social  progress,  upon 
Nature,  let  this  be  more  than  that  of  past 
or  passing  phases  and  groups,  but  of  the 
incipient  social  order  as  well,  of  Society  at 
its  very  best,  since  here  is  the  growing- 
point  of  our  own  evolution.  Yet  we  must 
test  all  anew  in  the  field;  for  by  our  fresh 
glimpse  of  theoretic  light,  the  whole  world 
must  be  reviewed  afresh,  and  our  new  light 
ray  tested  in  its  turn  for  all  it  may  be  worth, 
as  well  for  all  it  can  reveal.  The  true 
Darwinian  is  thus  not  he  who  longest  swears 
by  the  word  of  the  master,  and  stretches 
some  classic  adaptations,  say  of  flower  and 
insect,  towards  its  breaking  point,  but  he 
who  with  a  social  philosophy  advanced  be- 
yond that  of  Darwin's  teacher,  Malthus, 
goes  forth  anew  into  the  field.  For  one  this 
bettered  social  theory  may  be  Marx's,  for 
another  Ruskin's,  for  another  Gobineau's, 
Nietzsche's,  and  so  on:  each  is  actually 
yielding  its  biological  result.  Most  obviously 
perhaps,  Galton's,  since  his  studies  have 
been  again  of  the  population  question,  but 
in  what  new  light!     And  with  what  fresh 


ns  EVOLUTION 

results  and  impulses:  here  with  biometrician 
disciples,  there  with  no  less  active  Mendelian 
antagonists ! 

Yet,  as  we  have  seen,  it  is  not  enough  to 
be  students  even  of  Man  and  Nature;  we 
must  also  take  our  part  in  the  world  of  action, 
if  we  would  understand  the  action  of  life. 
The  scientist  has  affirmed  this  intensely  in 
his  insistence  on  field  work,  on  museum 
work,  on  laboratory  work:  but  still  too 
narrowly;  even  with  zoological  stations  and 
experimental  institutes  thrown  in.  Here  no 
preparation  can  be  too  full,  too  varied  in  its 
practicality. 

Explore  our  region  here,  and  any  other 
you  may  have  the  good  fortune  to  reach, 
fully,  thoroughly,  repeatedly,  from  hill- 
top to  sea-bottom  and  back  again.  Realize 
your  environment,  your  region  through 
activity  also:  and  this  not  only  as  an  ex- 
cursion-field, a  playing-field,  from  ski  to 
dive,  it  may  be  as  hunting-field  in  moderate 
measure,  but  as  work-field  also,  and  above 
all.  Go  down  into  mine  and  quarry;  get 
some  turn  at  hewing  coal,  at  dressing  stone. 
The  anvil,  the  joiner's  shop,  the  carver's  or 
other  studio  are  all  excellent;  already  com- 
ing into  use  for  afternoons  at  any  rate  of 
school  winters  in  town:  in  summers  be  out 
in   Nature;     see    and    touch   Nature    alive. 


EVOLUTION  THEORIES  228^ 

Go  out  then  with  the  herring-fleet  for  one 
summer's  holiday  at  least:  work  in  the  fields 
a  spring,  a  harvest,  and  tend  the  horse,  as 
well  as  hold  the  plough.  Work  too  in  the 
garden,  and  this  for  kitchen  as  well  as  for 
drawing-room;  yet  also  for  general  beauty 
as  well  as  detailed  use.  Above  all,  and  not 
only  for  culture's  sake  but  character's,  get 
out  with  the  shepherds,  till  you  know  not 
only  something  of  their  work,  but  of  them- 
selves. In  each  craft,  at  each  level,  learn 
not  only  something  of  the  immediate  work, 
but  of  its  workers,  and  of  their  ideal  aims, 
their  culture-spirit,  for  there  is  no  true 
work  and  no  true  worker  without  this:  then 
you  can  choose  your  occupation,  or  rather 
it  will  choose  you,  and  at  such  level  as  you 
may  be  fit  to  rise  to,  here  of  its  construc- 
tive toil  and  skill,  there  of  its  song  or  story, 
its  science  or  its  art. 

Rustic  and  Urban  as  contrasted  in 
Thought. — Of  all  the  many  occupational 
experiences  there  are  but  two  main  types, 
those  concerned  with  organic  and  with 
physical  nature,  the  rustic  and  the  urban,  I 
in  a  word,  the  vital  and  the  mechanical.  ' 
Here  is  the  main  contrast  of  town  and 
country,  in  their  characteristic  experiences, 
their  essential  occupations;  and  the  re- 
sultant   interpretative    evolutionary    stand- 


230  EVOLUTION 

points  which  we  are  seeking  will  be  essen- 
tially these  two,  will  be  characterized  by 
familiarity  with  the  processes  of  mechanism 
and  of  growth  respectively.  The  town  in- 
tellect is  of  course  the  swifter,  the  clearer, 
more  precise  and  definite,  the  more  assertive 
and  authoritative  accordingly;  hence  its 
characteristic  contributions  to  knowledge 
and  to  social  progress,  and  the  satisfaction 
with  which  it  proclaims  these,  and  with 
which  it  applies  these,  doubting  nothing,  to 
the  education  of  the  rustic  world,  which  un- 
doubtedly comes  forward  ficcordingly — but 
into  town.  That  surviving  slow,  heavy- 
footed  peasant,  behind  his  plough,  or  gazing 
over  the  fence  at  his  growing  corn — what 
blank  stupidity!  That  shepherd  striding 
back  from  the  snow-drift  with  the  lamb 
within  his  plaid — what  pretty  sentiment! 
That  is  what  the  mechanicals  and  moneyers 
I  and  paperists  of  cities  see  in  these  silent 
servitors  of  Life. 

Needed  Renewal  of  Rustic  Point  of 
View. — Suppose,  however,  that  they  one 
day  become  articulate;  that  Pasteur  is  not 
the  last  thinking  peasant,  but  an  initiative 
one,  a  forerunner,  already  followed  by  the 
breeders,  cultivators,  eugenists  of  previous 
pages.  With  such  contributions  to  the 
work  of  experimental  evolution  will  there 


,«; 


EVOLUTION  THEORIES  231 

not  also  be  forthcoming  corresponding  con- 
tributions to  its  theory?  This  will  be 
neither  in  terms  of  the  mere  mechano- 
morphism  of  the  physicists  and  chemists, 
nor  of  the  puzzled  mysticism  of  vitalist 
philosophers  as  yet  befogged  by  their  urban 
environments  or  bewildered  by  reaction 
from  it.  It  will  be  in  terms  of  biology 
proper,  and  its  processes,  of  nutrition  and 
reproduction,  of  metabolism  and  growth. 
Each  science  is  but  an  aspect  of  the  whole,  a 
pictured  facet  of  Nature's  unity,  but  it  has 
its  own  categories,  its  own  values.  No  one 
of  the  main  sciences,  be  they  the  objective — 
physical,  biological,  social;  or  the  sub- 
jective— ethic,  psychologic,  sesthetic — is  in- 
telligibly reducible  into  the  concepts  of  any 
other,  those  of  mechanics,  physics,  chemistry, 
despite  their  long  exaggerated  pretensions, 
as  little  as  any — (though  their  parallelisms 
may  and  should  be  sought;  that  is  a  practi- 
cable and  legitimate  inquiry).  It  tells  us 
nothing  of  the  aesthetic  value  of  scarlet 
blossom,  of  golden  sunset,  of  summer  green, 
that  these  have  such  and  such  relations  of 
wave-length,  interesting  in  the  physical 
laboratory  though  that  be.  By  all  means 
let  us  correlate  brain  growth  with  mind; 
but  the  life  of  intelligence,  idealism,  imagina- 
tion,   would   have   none   the   less   its   psy- 


232  EVOLUTION 

chological  independence  were  the  chemical 
formulae  of  every  brain  metabolism  pub- 
lished to-morrow. 

So  then  for  biology.  Its  theory  of  life,  of 
evolution  must  be  in  its  own  terms,  of  func- 
tion and  form,  and  free  therefore  from 
absorption  into  the  lower  physical  order,  as 
from  exaggeration  into  the  higher  ethical 
and  political  one.  The  latter  mode  of  state- 
ment is  the  transcendentalist's  old-fashioned 
fable;  the  former  is  a  materialistic  fable. 
But  to  correlate  and  parallelize  the  biological 
with  the  physical  order,  as  with  the  social, 
whenever  we  can:  that  is  a  different  matter. 

Above  all,  however,  let  us  as  naturalists 
see  that  we  grasp  not  only  the  mechanical 
and  urban  point  of  view  but  the  rustic  and 
physiological  one. 


CHAPTER  VIII 

THE  EVOLUTION  PROCESS  ONCE  MORE 
REINTERPRETED 

The  evolution  process  again  reinterpreted — Antithesis  of 
vegetation  and  reproduction;  applications  in  the  plant 
world — Justification  from  rustic  experience — Evolution  in 
the   animal   kingdom — Summary  and  conclusions. 

Though  we  must  leave  that  rich  mastery 
of  the  evolution  secret  we  once  hoped  for  to 
the  successors  we  would  fain  send  out  so 
much  better  equipped,  can  we  not  meantime 
be  going  at  least  a  step  or  two  farther  be- 
fore we  leave  life's  wonder-feast — readers 
and  writers  alike?  Here,  then,  in  preceding 
chapters  have  been  offered  summaries  and 
interpretations  not  a  few:  some  are  master- 
keys,  tested  by  long  and  world-wide  use, 
others  awaiting  trial  and  verification;  but 
most,  surely,  of  some  applicability.  In  con- 
clusion, and  not  as  dogmatically  pressed,  but 
suggestively  offered,  the  reader  may  be  inter- 
ested in  some  brief  outlines  of  a  different 
reinterpretation  of  the  evolution  process — 
one  not  as  yet  fully  published,  still  less 
seriously  criticized  by  other  biologists;  one 
suggested  at  the  close  of  our  "Evolution  of 

233 


234  EVOLUTION 

Sex,"  outlined  in  scattered  papers  and  lec- 
ture syllabuses,  and  with  its  beginnings 
compressed  into  a  too  dry  abstract  at  the 
close  of  the  old  "Britannica"  article  "Varia- 
tion and  Selection,"  many  years  ago. 

Let  us  start  from  the  acceptedly  known, 
from  Darwin's  natural  selection,  and  this  of 
"indefinite"  variations,  and  express  the  prob- 
lem before  us  in  the  words  of  Weismann: 
"We  certainly  cannot  remain  at  the  purely 
empirical  conception  of  variability  and  hered- 
ity as  laid  down  by  Darwin  in  his  admirable 
work.  In  the  first  enthusiasm  over  the  newly 
discovered  principle  of  selection,  the  one 
factor  of  transformation  contained  in  this 
principle  has  been  unduly  pushed  into  the 
background  to  make  way  for  the  other  more 
apparent  and  better  known  factors.  The 
first  indispensable  factor,  and  perhaps  the 
most  important  in  any  case,  in  every  trans- 
formation is  the  physical  nature  of  the  organ- 
ism itself." 

This  inquiry  into  the  organismal  springs 
of  variation  must  lead  us  far.  For  Weismann 
these  have  led  especially  into  his  subtle 
studies  of  the  germ-plasm;  but  obviously 
also  they  involve  a  fresh  survey  of  the  leading 
types  of  variation  as  we  see  them  developed 
by  plant  and  animal  forms.  Naturalists  are 
no  longer  so  much  setting  out  from  the  anal- 


THE  EVOLUTION  PROCESS        235 

ogy  of  human  selection  upon  domestic  ani- 
mals and  cultivated  plants,  and  reasoning 
from  the  accumulation  of  their  varietal 
differences  up  to  what  seem  to  correspond  to 
species  or  sometimes  even  genera  in  Nature, 
and  thence  arguing  on  Lyell's  uniformitarian 
principle,  for  the  analogous  cumulative  nat- 
ural selection  through  geological  time,  of  the 
characters  of  larger  groups,  genera,  orders, 
classes  and  the  rest.  We  have  simply  now 
to  group  our  types  of  variation,  and  to  con- 
sider them  from  the  standpoint  of  general 
physiology  as  far  as  we  know  it,  and  inde- 
pendently of  these  fascinating  hypotheses  of 
agriculture  and  geology. 

Vegetation  and  Reproduction,  and 
THEIR  Antithesis. — The  largest  view  of 
physiology,  one  peculiarly  obvious  to  the 
botanist,  from  the  vivid  distinctness  of 
flowers  and  foliage,  but  denied  by  none  for 
animals  and  man  as  well,  is  that  which  treats 
the  functions  of  living  beings  as  of  two  main 
kinds;  grouping  on  the  one  side  respiration, 
irritability,  and  all  the  other  activities  of  the 
individual  in  its  self-maintaining  life,  and 
then  setting  over  against  the  whole  of  these 
the  great  function  of  the  species-maintaining 
life,  reproduction.  Weismann's  main  work 
has  been  to  emphasize  this  distinction,  espe- 
cially from  the  side  of  the  intimate  morphol- 


236  EVOLUTION 

ogy  of  the  germ-cells;  while  some  of  the  best 
chapters  of  Spencer's  "Principles  of  Biology" 
are  those  in  which,  after  pointing  out  its 
intelligibility  in  terms  of  the  principle  of  con- 
servation of  energy,  he  elaborates  the  an- 
tithesis of  nutrition  and  reproduction  by 
reference  to  many  plant  and  animal  forms. 
Yet  though  the  principle  is  one  familiar 
since  the  dawn  of  physiology,  its  applica- 
tions are  still  far  from  exhausted.  "While 
philosophers  are  disputing  over  the  govern- 
ment of  the  world,  hunger  and  love  are  per- 
forming the  task,"  says  Schiller;  and  our 
"Evolution  of  Sex"  is  essentially  an  elabora- 
tion of  one  great  aspect  of  this  theme. 

Applications  towards  Interpretation 
OF  THE  Plant  World. — Let  us  begin  with 
the  origin  of  the  flower,  which  all  agree  in 
regarding  as  a  shoot  modified  for  reproduc- 
tion. But  it  is  also  shortened,  as  compared 
with  a  vegetative  shoot;  then  why.^^  By 
natural  selection  from  two  other  alternative 
variations  .f^ — one  like  the  vegetative  shoot, 
and  the  other  lengthened  farther  still.?  These 
are  imaginable  as  forms;  there  is  no  mor- 
phological absurdity  about  them:  yet  we 
may  be  fairly  sure  they  never  existed  at  all, 
and  so  have  not  been  selected.  How  so.^^ 
They  are  excluded  by  the  physiological 
explanation  of  inevitable  shortening;    since 


THE  EVOLUTION  PROCESS        237 

the  organic  expenses  of  the  onset  of  the 
reproductive  function  necessarily  check  the 
vegetative  ones. 

Similarly  for  flower  groupings,  the  "forms 
of  inflorescence."  The  simplest  form  is  the 
long  flowery  stem,  each  flower  with  its  own 
stalk,  like  the  foxglove  spire;  but  such  fine 
"racemes"  are  comparatively  uncommon. 
Often  the  flower-stalks  are  arrested,  and  we 
have  the  "spike,"  as  in  the  mullein,  golden- 
rod;  or  again  it  may  be  the  main  stem  which 
stops  short,  leaving  the  minor  stalks  to  grow 
and  separate  the  flowers,  as  in  the  "umbel" 
of  cowslip  (and  even  primrose),  of  ivy  and  of 
the  parsley  and  hemlock  tribe  without  num- 
ber. But  in  one  great  order,  and  that  sig- 
nificantly one  of  the  most  successful  in  the 
whole  world-flora,  the  daisy  and  dandelion 
order,  the  axis  of  inflorescence  is  arrested  in 
growth  until  it  is  a  flat  disk,  and  the  flower 
stems  have  disappeared  altogether,  so  that 
we  have  the  crowded  "head"  of  flowers, 
their  own  individual  development  greatly 
reduced,  so  characteristic  of  the  Composites. 
This  principle  of  flower-heading  is  constant 
in  not  a  few  orders  otherwise  widely  distinct, 
like  willows  and  plantains;  and  appears  here 
and  there  among  other  orders,  e.g.  in  sea- 
pinks,  and  even  among  labiates  and  rose- 
worts.    It  is  noticeable  that  such  forms,  like 


238  EVOLUTION 

the  Composites  themselves,  are  commonly 
vigorous  and  hardy  growers,  as  may  reason- 
ably happen,  the  saving  through  subordina- 
tion of  the  reproductive  shoots  being  appli- 
cable to  help  on  the  vegetative  ones.  In  the 
figs,  a  peculiarly  vigorous  and  varied  tribe, 
the  arrest  of  the  inflorescence  goes  so  far  as 
to  make  this  like  an  inturned  glove-finger, 
a  hollow  pouch  instead  of  the  usual  ascend- 
ing cone,  and  with  the  tiny  florets  inside 
accordingly. 

Now,  returning  to  the  individual  flower, 
it  is  an  interesting  fact  that  this  process  of 
reduction  of  the  great  axis  of  inflorescence 
from  shoot  to  head,  and  thence  to  fig,  is 
repeated  on  that  small  axis  of  the  flower, 
which  the  beginner  in  flower  dissection  is  apt 
to  forget  altogether.  This,  however,  may  be 
easily  made  out  as  a  distinct  case,  in  the 
buttercup,  or  best  of  all,  in  the  magnolia,  and 
the  sepals  and  petals,  the  stamens  and  carpels, 
may  all  be  seen  to  arise  upon  this  in  ascend- 
ing order,  like  the  young  crowded  leaves  of 
a  vegetative  bud.  This  simple  ("hypogy- 
nous")  arrangement,  however,  goes  farther 
in  the  ("perigynous")  strawberry,  where, 
instead  of  a  short  conical  shoot,  we  have 
now  the  axis  disk-shaped,  recalling  the  com- 
posite head;  while  even  the  hollow  fig 
finds  its  parallel  in  the  many  flowers  which, 


THE  EVOLUTION  PROCESS        239 

like  rose  or  daffodil,  have  become  "epigy- 
nous,"  i,e.  with  their  ovaries,  now  sunk  at 
the  bottom  of  a  cup,  the  arrested  and  over- 
grown apex.  Passing  now  to  forms  so  utterly 
distinct  as  the  fungi,  we  find  the  same  proc- 
ess repeating  itself,  the  essential  reproduc- 
tive organs  sinking  from  cone  to  disk,  and 
thence  into  cup  or  pouch,  like  fig  and  rose, 
indeed  closing  up  completely. 

Now,  the  farther  we  go  in  our  studies  of 
flower  anatomy,  the  more  we  find  of  this 
subordination  of  the  vegetative  life  by  the 
reproductive;  witness  the  reduction  of  the 
number  of  petals,  stamens  and  carpels  from 
indefinite  to  few.  See,  however,  what  all 
this  amounts  to.  All  these  changes  and 
others,  in  fact  the  most  important  of  floral 
variations,  the  big  lifts  distinctive  for  the 
evolution  of  orders,  are  thus  seen  no  longer 
as  indefinite,  and  hence  dependent  on  ex- 
ternal selection  for  their  guidance;  but,  on 
the  contrary,  as  parallel  and  definite,  since 
determined  through  the  continued  checking 
of  the  vegetative  process  by  the  reproductive, 
and  thus  pressed  along  parallel  and  definite 
grooves  of  progressive  change.  But  if  this 
be  so,  the  importance  we  have  been  taught 
by  Darwin  to  assign  to  natural  selection 
becomes  greatly  changed — from  selecting  and 
accumulating  supposed  indefinite  variations. 


240  EVOLUTION 

to  that  mainly  of  retarding  definite  ones, 
after  their  maximum  utility  has  been  in- 
dependently reached! 

The  same  simple  conception  unlocks  innu- 
merable problems  of  floral  morphology,  large 
and  small  alike,  from  the  inevitable  develop- 
ment of  angiosperm  from  gymnosperm  (by 
the  continuous  subordination  in  vegetative 
development  of  the  reproductive  carpellary 
leaf)  to  the  origin  of  many  of  the  refined 
minor  "adaptations"  of  the  dominant  school. 
Adaptation  to  insects,  to  wind  also,  thus  falls 
from  a  primary  to  at  most  a  very  secondary 
place  as  a  factor  in  the  evolution  of  fiowers; 
for  the  characteristics  usually  ascribed  to 
the  selective  action  of  wind  and  insects 
constantly  appear  at  the  extremes  of  the 
relatively  more  vegetative  and  more  floral 
series  which  are  discernible  more  or  less  in 
every  alliance,  great  and  small.  Witness 
among  the  vast  group  of  monocotyledons, 
the  extremes  of  the  grasses  and  the  orchids 
respectively;  or  in  a  single  genus,  say 
Senecio,  its  weedy  groundsels  and  gorgeous 
cinerarias. 

Justification  of  the  Present  Theory 
IN  Rustic  Experience. — Now  this  whole 
theoretic  reinterpretation :  whence  is  it.^ 
Again  from  experience.  With  the  resources 
of  a  great  garden,  at  any  rate  with  a  gardener 


THE  EVOLUTION  PROCESS        241 

to  do  all  the  work  for  us,  we  come  out  at 
leisure,  and  notice  the  flowers,  here  visited 
by  insects,  and  there  swaying  in  the  wind, 
and  fancy  their  forms  thus  fashioned,  adapted, 
selected  from  without;  our  town  friends 
are  readily  convinced  of  this,  and  their 
assent  strengthens  our  convictions  and  stimu- 
lates our  researches  anew.  But  when  we 
set  about  making  a  garden  for  ourselves,  and 
labour  with  our  own  hands,  new  perspectives 
open,  fresh  points  of  view  appear,  above  all 
that  of  growth;  and  this — even  at  its  very 
simplest,  the  wide  growth-contrast  of  lilies 
and  rushes,  of  weeds  and  flowers — reinter- 
prets the  differences  we  formerly  ascribed  to 
form — as  scientists  we  thought,  as  leisure 
class  we  now  see;  and  essentially  urban  at 
that.  For  while  in  our  tovA^n  herbaria  we 
distinguish  grasses  and  orchids  essentially  by 
their  post-mortem  structure,  the  gardener 
is  the  fuller  scientist,  the  true  physiologist, 
knowing  their  differences  as  lives;  the  grass 
so  vegetative  that  cattle  and  farm  and  city 
all  live  upon  its  surplus,  the  orchids  so 
splendidly  floral  that  we  may  easily  spend 
upon  their  culture  more  than  our  grass-field 
can  earn. 

If  this  rustic  point  of  view  be  seized,  and 
the  urban  and  mechanical  one  correspond- 
ingly subordinated,  the  present  theory   will 


242  EVOLUTION 

work  itself  out  just  as  fully  and  freshly  as 
did  the  selectionist  game  of  thought:  if  not, 
it  remains  useless  to  argue  for  it.  The  eye 
sees  only  what  it  brings  the  means  of  seeing. 

Re-interpretation  of  the  Animal  King- 
dom.— Instead  then  of  opening  new^  botanical 
sections,  of  which  each  would  really  require 
a  chapter,  sometimes  a  whole  volume,  now 
dealing  with  the  interpretations  of  flowers 
and  of  fruits,  and  again  with  the  great  pecu- 
liarities of  habit — evergreens,  thorny  plants, 
climbers  and  so  on,  let  us  rather  ask:  Can 
any  such  physiological  interpretations  be 
applied  to  a  survey  of  the  animal  kingdom? 
Its  problems  are  obviously  far  more  intricate 
and  varied:  yet  the  result  is  scarcely  less 
definite  or  comprehensive.  In  the  outline 
of  our  restatement  of  the  cell-theory  as  a 
"theory  of  the  cell  cycle"  (Chapter  III)  we 
have  already  interpreted  such  main  forms  of 
Protozoa  as  the  rhizopods,  the  gregarines,  the 
infusors,  not  from  without,  as  the  empirically 
selected  products  of  spontaneous  variations 
among  indefinite  possibilities,  but  from  with- 
in, as  simply  the  preponderatingly  amoeboid, 
resting,  and  motile  phases  of  the  cell-cycle, 
three  forms  determined  by  the  properties  of 
protoplasm  itself. 

This  conception  of  life-histories,  as  physio- 
logical  and   not   merely    structural,  ration- 


THE  EVOLUTION  PROCESS       243 

alizes  our  animal  no  less  than  our  vegetable 
classifications.  Thus  the  greatest  of  all  steps 
in  morphological  progress,  that  from  the  uni- 
cellular Protozoa  to  the  multicellular  Meta- 
zoa,  is  plainly  not  due  to  the  external  selec- 
tion of  the  more  individuated  and  highly 
adapted  Protozoan  species,  but  is  under- 
stood from  within,  as  the  union  of  relatively 
embryonic  and  unindividuated  cells  into  an 
aggregate  in  which  each  becomes  diminish- 
ingly  competitive  as  regards  its  fellows,  and 
increasingly  subordinated  to  the  social  whole; 
while  within  the  body  thus  developed,  a 
series  of  cells  remains  relatively  undiffer- 
entiated as  the  essential  sex  organ,  female  or 
male  (preponderatingly  anabolic  or  katabolic) 
as  the  case  may  be.  And  as  the  natural 
variations  and  divergences  of  plants  may  be 
most  conveniently  summed  in  terms  of  vege- 
tative and  floral  preponderance  respectively, 
so  those  of  animals  similarly  fall  into  the 
broadly  recognizable  contrast  of  passive  and 
active,  sedentary  and  errant,  perpetually 
renewing  itself  in  every  group.  Hence  the 
contrast  of  fixed  anenome  or  coral  and  swim- 
ming jelly-fish  or  ctenophore,  of  stony  tube- 
worms  and  naked  creeping  or  swimming 
worms,  or  the  contrast,  yet  series,  of  fixed 
crinoid  and  boring  urchin  with  creeping  star- 
fish and  active  sand-star;  or  again  of  passive 


244  EVOLUTION 

barnacle  and  active  shrimp,  of  sluggish 
beetle  and  nimble  gnat;  or  again  within  the 
same  orders,  as  moth  and  butterfly — always 
the  same  dichotomy  of  passive  and  active. 
Here  essentially  lies  the  secret  of  the  diver- 
gence between  ascidian  and  vertebrate,  to 
take  a  great  difference,  or  that  between  toad 
and  frog  for  a  small  one;  or  again  this  is  the 
main  contrast  between  reptile  and  bird, 
Diplodocus  and  swallow.  This  lies  within 
the  perpetual  redifferentiation  of  these, 
witness,  among  reptiles,  the  sluggish  and 
often  colossal  tortoises,  yet  the  active  and 
supple  snakes;  and  these  (of  course)  again 
differentiating  anew,  here  the  huge  and 
passive  python,  and  there  the  small  and 
nimble  fer  de  lance.  Once  more,  for  birds, 
see  the  contrast  of  the  massive  pedestrian 
dodo  with  his  pigeon  cousins;  or  of  giant 
chickens  like  the  ostrich  and  emu  tribes  with 
exquisite  but  tiny  adults,  say  the  humming- 
birds. The  kinship  of  elephant  and  coney, 
the  contrast  of  stony  glyptodon  and  gigantic 
sloth  with  nimble  lemur  and  agile  monkey, 
and  again  of  bear  and  dog,  of  dog  and  cat, 
of  sheep  and  goat,  are  thus  re-interpreted 
together,  no  longer  as  for  the  early  Darwin- 
ians as  so  many  machine-like  combinations 
of  innumerable  indefinite  variations  exter- 
nally selected  from  among  yet  more  innumer- 


THE  EVOLUTION  PROCESS        245 

able  ones,  nor  even  among  a  more  limited 
number  of  ancestral  possibilities,  but  as  so 
many  forms  thrown  from  the  rhythmic 
oscillation  of  the  loom  of  life.  Each  of  these 
types  or  species,  with  its  exquisite  intricacy 
of  detail  and  individuality  of  pattern,  its 
marvellous  correlation  of  organs,  is  thus  a 
new  unity  created  from  within  by  its  own 
interior  play  and  balance  of  vegetative  and 
reproductive  forces,  its  inner  predominances 
here  of  anabolisms  and  there  of  katabolisms. 
Growth  and  arrest,  giant  and  dwarf,  rest 
and  movement,  sleep  and  waking,  even  fe- 
male, and  male  are  contrasts  all  physiologi- 
cally akin;  and  this  single  and  simple  rhythm 
of  metabolisms,  of  passivities  and  activities 
goes  on  into  compound  and  recompounding 
rhythms,  like  the  figures  of  the  pendulo- 
graph.  The  forms  of  life  are  thus  distinct 
and  definite,  because  harmoniously  unified. 
They  have  a  certain  stability,  great  or  small, 
yet  they  are  anew  transf orinable,  like  musical 
variations,  like  singing  flames.  Thus  from 
within  are  spun  and  woven  and  shaped  the 
manifold  garments  of  Life,  always  simple, 
though  ever  more  and  more  Protean.  Our 
clue  to  the  secret  of  variational  evolution 
thus  holds  good,  is  one  and  the  same  from 
the  ancient  contrast  of  plant  and  animal  up 
through  the  great  lifts  of  evolution,  and  down 


246  EVOLUTION 

through  its  ever  recurrent  falls;  and  if  it 
applies  equally  to  the  origin  of  classes  and 
orders,  of  genera  and  of  species,  why  not  also 
to  the  varieties  and  mutations  which  natural- 
ists are  discussing,  for  the  most  part  too 
externally,  at  the  present  day? 

Summary  and  Conclusions. — As  in  plants 
the  species-maintaining  functions  prepon- 
derate over  the  individual  ones,  so  that 
from  annual  to  agave  the  plant  must  flower 
although  it  die,  so  the  same  preponderance 
appears  in  animals.  The  "self-interest"  in 
which  the  utilitarian  economists  found  the 
all-sufficient  spring  of  action,  and  which 
naturalists  too  long  and  too  uncritically 
adopted  from  these  (whence  Huxley's  "glad- 
iator's show"),  turns  out  to  be  enlightened 
by  family  interest,  species  interest,  however 
sub-conscious.  The  traditional  primary 
insistence  upon  the  individual  competition 
for  food,  and  the  very  subordinate  and  tardy 
recognition  of  the  importance  of  sexual  and 
social  co-operation,  are  also  traceable  to  a 
confusion  of  thought — that  of  putting  the 
nutritive  factor  "in  the  first  place"  because 
it  precedes  the  reproductive  in  time;  whereas 
the  organism  enters  upon  reproduction, 
and  so  cedes  the  preponderance,  "the  first 
place,"  to  the  species-regarding  functions. 
That  increase  of  the  reproductive  sacrifice 


THE  EVOLUTION  PROCESS        247 

which  first  makes  the  mammal,  and  then 
marks  each  of  its  distinctive  upKfts  of  further 
progress  (from  monotreme  to  marsupial, 
and  thence  to  placental),  that  increase  of 
parental  care,  that  frequent  appearance  of 
sociality  and  co-operation  which,  even  in  its 
rudest  forms,  so  surely  secures  the  success 
of  the  species  attaining  it,  be  it  mammal  or 
bird,  insect  or  even  worm — all  these  survivals 
of  the  truly  fittest,  through  love  and  sacri- 
fice, sociability  and  co-operation  simple  to 
complex — need  far  other  prominence  than 
they  can  possibly  receive  even  by  some  mil- 
dewing attenuation  of  the  classic  economic 
hypothesis  of  the  progress  of  the  species 
essentially  through  the  internecine  struggle 
among  its  individuals  at  the  margin  of 
subsistence. 

Our  theory  thus  furnishes  a  re-interpreta- 
tion of  the  forms  attained  by  plants  and 
animals  comparable  to  that  afforded  by  the 
received  hypothesis  (and,  if  space  allowed, 
traceable  into  no  less  refinement  of  detail), 
yet  with  an  essentially  allied  view  of  the 
process  and  factors  of  organic  evolution  as  a 
whole.  Most  briefly  stated,  the  view  of  evo- 
lution thus  reached  is  that  of  definite  varia- 
tion: its  branchings  essentially  dichotomous 
rather  than  indefinite,  with  progress  essen- 
tially through  the  subordination  of  individual 


248  EVOLUTION 

struggle  and  development  to  species-main- 
taining ends.  The  ideal  of  evolution  is  thus 
no  gladiator's  show,  but  an  Eden;  and  though 
competition  can  never  be  wholly  eliminated — 
the  line  of  progress  is  thus  no  straight  line 
but  at  most  an  asymptote — it  is  much  for  our 
pure  natural  history  to  see  no  longer  struggle, 
but  love  as  "creation's  final  law." 

Natural  selection  remains  still  a  vera  causa 
in  the  origin  of  species;  but  the  function 
ascribed  to  it  is  practically  reversed.  It 
exchanges  its  former  supremacy  as  the 
supposed  sole  determinant  among  practically 
indefinite  possibilities  of  structure  and  func- 
tion, for  the  more  modest  position  of  simply 
accelerating,  retarding  or  terminating  the 
process  of  otherwise  determined  change.  It 
furnishes  the  brake  rather  than  the  steam  or 
the  rails  for  the  journey  of  life;  or  in  better 
metaphor,  instead  of  guiding  the  ramifica- 
tions of  the  tree  of  life,  it  would,  in  Mivart's 
excellent  phrase,  do  little  more  than  apply 
the  pruning-knife  to  them.  In  other  words, 
its  functions  are  mainly  those  of  the  third 
Fate,  not  the  first;  of  Siva,  not  of  Brahma. 


PmKXTY  UMAMt 


BIBLIOGRAPHY 


This  list  of  books  has  been  made  longer  than  in  most  of 
the  volumes  of  the  series,  and  for  three  reasons.  (1)  The 
scientific  study  of  organic  evolution  is  still  very  young.  There 
are  many  uncertainties,  there  is  rapid  progress  along  diverse 
lines,  there  are  not  a  few  moot  and  controversial  points.  We 
wish  to  recognize  this  by  giving  a  representative  set  of  refer- 
ences, indicative  of  various  schools  of  evolutionists.  (2)  We 
have  met,  personally  and  in  correspondence,  a  large  number 
of  able-minded  workers — face  to  face  with  evolution  problems, 
e.g.  as  breeders  or  as  gardeners,  as  medical  practitioners  or 
travellers — who  had  thought  long,  and  sometimes  carefully, 
over  particular  sets  of  facts,  but  remained  entirely  unaware 
that  these  had  been  threshed  out,  not  once  or  twice,  but 
many  times  over.  Not  that  this  refuses  value  to  any  new 
observation  or  thought,  but  it  suggests  that  some  literary 
research  may  be  reasonably  expected  from  those  who  have 
reached  what  they  feel  sure  is  an  upsetting  conclusion.  We 
hope  that  this  little  book  and  this  list  will  facilitate  that 
research.  (3)  The  problem  of  Becoming  is  not  particular  to 
any  one  science.  It  is  social  as  well  as  cosmic  and  organic. 
Therefore  in  our  list  we  have  not  forgotten  that  Darwinism 
touches  the  Humanities. 

*  Those  marked  with  one  asterisk  may  be  the  best  books 
for  a  student  to  begin  with.  But  the  best  beginning  is  always 
where  the  personal  tendril  fixes. 

**  Those  marked  with  two  asterisks  record  important  post- 
Darwinian  investigations. 

It  is  too  difficult  to  aSix  marks  to  suggestive  thoughts — 
shall  we  say  of  Bergson,  for  instance — which  may  turn  out  to 
be  of  much  more  value  than  many  concrete  studies.  The 
idea  of  confining  "research"  to  the  objective  is  grotesque. 

***  Those  marked  with  three  asterisks  are  "classics." 

Bailey,  L.  H.— "Plant-breeding."  3rd  Edition,  1904.  [A 
valuable  and  practical  study  of  variation  and  selection 
in  cultivated  plants.]  See  also  "The  Survival  of  the 
Unlike."     1896. 

Baldwin,  J.  Mark. — "Development  and  Evolution."  1902. 
[Expounds  the  author's  theory  of  the  indirect  evolu- 

249 


250  BIBLIOGRAPHY 

tionary  importance  of  modifications.]  See  also  "Darwin 
and  the  Humanities."     1909. 

**Bateson,  W. — "Materials  for  the  Study  of  Variation." 
1894.  [A  remarkable  collection  of  data  relating  to  certain 
kinds  of  variation,  especially  important  in  its  evidence 
of  discontinuous  variation;  a  book  to  consult  and  to 
reckon  with,  rather  than  to  read,  but  with  a  stimulating 
introduction.] 

1' The    Methods   and    Scope   of    Genetics."      1908.      [An 

illuminating  introductory  lecture,  suggesting  to  an  edu- 
cated reader  something  of  the  import  and  the  fascination 
of  Mendelian  experiments,  by  which  the  author  has 
acliieved  much.] 

** — ^"  Mendel's  Principles  of  Heredity."  1909.  [The  most 
important  statement  of  what  has  been  achieved  by  the 
experimental  study  of  genetics.] 

Bergson,  Henhi. — "Creative  Evolution."  1911.  Translation 
of  "L'Evolution  creatrice."  1907.  [One  of  the  most 
profound  and  original  contributions  to  the  philosophical 
consideration  of  the  theory  of  evolution.] 

Butler,  Samuel. — "Evolution:  Old  and  New."  2nd  Edition, 
1882.  [A  keen-witted  criticism  of  orthodox  Darwinism.] 
See  also  "Life  and  Habit."  1878.  [Strong  statement 
of  Lamarckian  views.]    "Luck  or  Cunning."     1887. 

*Clodd,  E. — "Story  of  Creation,  a  plain  account  of  Evolu- 
tion."   1888.    [A  useful  introduction.] 

"Pioneers  of  Evolution,"      1897.      [A  very  interesting 

historical  sketch.] 

CoE,  C.  C. — "Nature  versus  Natural  Selection."  [Extreme 
position,  denying  the  efficacy  of  Natural  Selection.] 

Conn,  H.  W.— "Method  of  Evolution."     1900. 

Cope,  E.  D. — "The  Primary  Factors  of  Organic  Evolution." 
1896.  [Strong  exposition  of  Lamarckian  and  bathmist 
position.]    /See  aZso  "The  Origin  of  the  Fittest."     1887. 

**CuENOT,  L. — "La  Gen^se  des  especes  animales."  1911. 
[A  masterly  book,  giving  a  fresh  and  careful  account  of 
the  present  state  of  knowledge  in  regard  to  the  origin 
of  animal  species.] 

***Darwin,  Charles.— " Origin  of  Species"  (1859);  "Varia- 
tion of  Animals  and  Plants  under  Domestication" 
(1868);  "Descent  of  Man"  (1871). 

Davenport,  C.  B. — "Experimental  Morphology."  1897.  [A 
valuable  uncompleted  treatise  on  the  plasticity  and 
modifiability  of  the  organism.] 

"Statistical  Methods  in  the  Study  of  Variation."     2nd 

Edition,  1904.    [A  useful  introduction  to  biometrics.] 


BIBLIOGRAPHY  251 

**Davenport,  C.  B. — "Inheritance  in  Poultry."  1906.  [A 
fine  series  of  experiments  in  breeding.] 

**Delage,  Yves. — "L'Heredite  et  les  grands  probl^mes  de  la 
biologie  generale."  1895;  2nd  Edition,  1902.  [A  great 
book,  discussing  with  scholarship  and  impartiality  the 
chief  problems  of  biology;  Lamarckian  on  the  whole 
and  against  Weismann;  with  a  detailed  bibliography.] 
See  also  an  excellent  short  book  by  Delage  and  Goldsmidt, 
"Les  Theories  de  L'Evolution."    1809. 

Deperet,  C. — The  Transformations  of  the  Animal  World." 

1909.  [A  useful  concrete  study  of  the  actual  history  of 
the  past.] 

*DoNCASTER,  L. — "Heredity  in  the  light  of  recent  Research." 

1910.  [A  pithy  and  clear  introduction.] 

Driesch,  Hans. — "Science  and  Philosophy  of  the  Organism." 
GifTord  Lectures  in  the  University  of  Aberdeen.     2  vols., 

1908.  [A  deep  and  original  vindication  of  vitalism,  diffi- 
cult for  most  readers;  a  fine  gymnasium  for  intellectual 
athletes.] 

EiMER,  G.  H.  Th. — "Organic  Evolution."  1890.  [Lamarckian 
and  Goethian,  with  a  theory  of  orthogenesis,  or  progres- 
sive variation  along  a  definite  line.] 

**EwART,  J.  CossAR. — "  Pcnycuik  Experiments."  1899.  [An 
account  of  important  breeding  experiments  bearing  on 
hybridization,  reversion,  variation,  etc.] 

''Fifty  Years  of  Darwinism:  Modern  Aspects  of  Evolution." 
Centennial  addresses  in  honour  of  Charles  Darwin  before 
the  American  Association  for  the  Advancement  of  Science, 

1909.  [An  exceedingly  interesting  and  valuable  series  of 
lectures  on  Darwinism,  by  numerous  authorities.] 

***Galton,  Francis.— "  Natural  Inheritance."  1889.  [A 
classic  book,  applying  statistical  methods  to  the  study 
of  inheritance,  and  expounding  important  generalizations, 
such  as  Filial  Regression.] 

Geddes,  Patrick. — "Variation  and  Selection"  in  "Encyclo- 
paedia Britannica,"  9th  Edition.  "Darwinian  Theory," 
' '  Evolution, "  in  "  Chambers's  Encyclopaedia."  * '  Chapters 
in  Modern  Botany."     1893. 

Geddes,  P.,  and  Thomson,  J.  Arthur. — "The  Evolution  of 
Sex."  1889.  Revised  Edition,  1901.  [A  discussion 
of  sexual  selection,  the  reproductive  factor  in  evolution, 
the  physiological  interpretation  of  sex,  and  so  forth. 
The  general  thesis  is  that  maleness  and  femaleness  are 
expressions  of  alternatives  in  the  regulated  rhythm  of 
metabolism.] 

Geoos,  K.— "The  Play  of  Animals."  Translation,  1900.  [A 
very  suggestive  book,  a  proof  of  the  biological  importuuce 


252  BIBLIOGRAPHY 

of  play,  with  an  important  contribution  to  the  theory  of 
sexual  selection.] 

GuLiCK,  J.  T. — "Evolution,  Racial  and  Habitudinal."  1905. 
[Elaborate  discussion  of  isolation  as  a  factor  in  evolution.] 

***Haeckel,    Ernst. — "Generelle    Morphologic."     2    vols., 
1866.      [A   classic  work,   to   be  placed   beside   Spencer's 
"Principles  of  Biology."    It  is  now  out  of  print,  but  part 
1  of  it  has  been  recently  re-issued.] 

"Natural    History    of    Creation."      English   translation, 

1870.  [A  picturesque  book  that  has  passed  through 
many  editions.  The  early  chapters  give  a  vivid  account 
of  the  rise  of  the  evolution  theory.  The  statement  of 
"the  evidences"  had  a  deserved  success  in  vindicating 
the  validity  of  the  evolution  formula.] 

*Headley,  F.  W.— "Life  and  Evolution."  1906.  [Pictur- 
esque concrete  illustrations  of  the  problems  of  evolution.] 
See  also  "Problems  of  Evolution."     1900. 

HuTTON,  F.  W. — "Darwinism  and  Lamarckism."     1899. 

Huxley,    T.    H. — Article    "Evolution"   in    "Encyclopaedia 

Britannica,"  9th  Edition. 
*** "American  Addresses."     (1877.) 

Jenkinson,  J.  W.— "Experimental  Embryology."  1909.  [A 
very  able  treatise  on  the  external  and  internal  factors  in 
development.  With  a  valuable  discussion  of  Vitalism 
and  Driesch's  contributions  thereto.] 

**JoHANNSEN,  W. — "  Uebcr  Erblichkeit  in  Populationen  und 
in  reinen  Linien."  1903.  [Important  experiments  on 
beans,  barley,  etc.;  notably  on  the  isolation  of  "piire 
hues."]  See  also  "Die  Elemente  der  exakten  ErbHch- 
keitslehre."     1909. 

Jordan,  D.  S.,  and  Kellogg,  V.  L. — "Evolution  and  Animal 
Life."  1907.  [Very  interesting  concrete  studies  of 
evolution  problems.] 

Kellogg,  V.  L.— "Darwinism  To-day."  1907.  [A  remark- 
able book,  with  the  frankest  and  friendliest  reconsidera- 
tion of  Darwinism,  in  the  light  of  post-Darwinian  progress, 
by  a  thoroughly  competent  critic.  With  abundant 
references  to  and  quotations  from  recent  evolutionary 
literature.] 

Kropotkin,  p. — "  Mutual  Aid  a  Factor  of  Evolution."  1902. 
[A  valuable  account  of  the  inadequately  appreciated 
"other  side"  of  the  struggle  for  existence.] 

Lankester,  E.  Rat. — "The  Advancement  of  Science."  1890. 
[Important  essays  on  "Degeneration:  a  chapter  in  Dar- 
winism," "A  Theory  of  Heredity,"  "The  History  and 
Scope  of  Zoology,"  etc.]  See  also  "The  Kingdom  of 
Man."     1906. 


BIBLIOGRAPHY  253 

♦Lock,  R.  H.— "Recent  Progress  in  the  Study  of  Variation, 
Heredity,  and  Evolution."  1908.  [A  useful  introduction 
to  recent  researches.] 

LoTSY,  J.  P. — "  Vorlesungen  iiber  Descendonztheorie."  2  vols. 
1907  and  1909.    [A  scholarly  text-book  of  evolution.] 

♦Marshall,  A.  Milnes. — "Lectures  on  the  Darwinian 
Theory." ^  1894.  [An  admirably  clear  and  vigoroua 
presentation  of  Darwinism  and  of  the  evidences  of  evo- 
lution.] See  also  "Biological  Lectures  and  Addresses." 
1894. 

Marshall,  F.  H.  A.— "The  Physiology  of  Reproduction." 
1910.  [A  masterly  work  with  many  bearings  on  evolution 
problems.] 

Merz,  J.  T.— "History  of  Scientific  Thought  in  the  Nine- 
teenth Century."  2nd  vol.,  1904.  [The  finest  exposition 
of  the  import  and  development  of  "the  genetic  view  of 
Nature."  A  work  of  magistral  scholarship  and  deep 
insight.] 

♦Metcalf. — "Outline  of  the  Theory  of  Organic  Evolution." 
1904.     [A  useful  introduction.] 

**]V[oKGAN,  C.  Lloyd.— "Habit  and  Instinct."  1896.  [The 
most  important  book  on  instinct.]  See  also  "Animal 
Life  and  Intelligence"  (1890);  revised  edition,  entitled 
"Animal  Behaviour."     1900. 

Morgan,  T.  H.— "Evolution  and  Adaptation."     1903.     [An 

important  critical  essay.] 
** "Experimental    Zoology."      1907.      [An  indispensable 

account   of   recent   experimental   researches   bearing   on 

evolution.      A    worthy    supplement    to    Semper's    great 

work,  "Animal  Life."] 

Nageli,  C.  von.  —  "  Mechanisch-physiologische  Theorie  der 
Abstammungslehre."  1884.  [The  most  effective  pres- 
entation as  yet  given  of  the  theory  of  organismal  vari- 
ation in  definite  directions.] 

OsBORN,  H.  F.— "From  the  Greeks  to  Darwin."  1895.  [A 
vivid  historical  sketch.] 

Packard,  A.  S. — "Lamarck,  his  Life  and  Work."  1901.  [A 
scholarly  account  of  Lamarck's  theory  of  evolution.] 

**Pearson,  Karl. — "The  Grammar  of  Science."  2nd 
Edition,  1900.  [The  biological  part  includes  an  invalu- 
able discussion  of  evolution  problems  from  the  biometri- 
cian's  point  of  view.] 

Perrier,  E. — "  Philosophic  zoologique  avant  Darwin."  1884. 
[A  scholarly  account  of  pre-Darwinian  evolutionists  and 
generalizers.] 

♦Plate,  L. — "  Selektionsprinzip  und  Probleme  der  Artbildung. 
Ein  Handbuch  des  Darwinismus."      3rd  Edition,   1908. 


254  BIBLIOGRAPHY 

[A  scholarly  and  lucid  text-book  of  evolution^  in  part 
Lamar  ckian.] 

**PouLTON,  E.  B.— "Essays  on  Evolution,  1889-1907." 
1908.  [Very  valuable  critical  and  historical  studies,  and 
applications  of  the  theory  of  evolution  to  mimicry  and 
protective  coloration  in  insects.] 

* "Charles  Darwin  and  the  Theory  of  Natural  Selection." 

1896. 

**Przibram. — Experimental  Zoology,  Part  I,  Trans.  1908. 
[Acute  discussion  by  an  expert  investigator  of  the  results 
of  experimental  embryology.] 

*PuNNETT,  R.  C— "Mendelism."  2nd  Edition,  1905.  [An 
unsurpassed  exposition  by  an  expert  investigator.] 

Radl,  Em. — "Geschichte  der  biologischen  Theorien."  2nd 
Part,  1909.  [An  able  historical  and  critical  discussion 
of  biological  theories  and  of  Darwinism  in  particular.] 

Reid,  G.  Archdall. — "The  Laws  of  Heredity."  1910.  See 
also  "The  Principles  of  Heredity."     1906. 

RiGNANO,  E. — "Ueber  die  Vererbung  erworbener  Eigen- 
schaften."  1907.  [A  careful  discussion  of  the  question  of 
the  transmission  of  acquired  characters.] 

Romanes,  G.  J. — "Darwin  and  after  Darwin."  3  vols.,  1892- 
97.  [A  valuable  exposition  of  Darwinism  with  many 
original  suggestions  and  criticisms,  and  with  an  important 
discussion  of  isolation.] 

Schneider,  K.  C. — "Einfiihrung  in  die  Descendenz-theorie." 
1906.  [A  fresh  and  lucid  statement  of  the  evidences  of 
evolution,  with  a  short  account  of  the  chief  theories.] 

Semon,  R. — "Die  Mneme  als  erhaltendes  Princip  im  Wechsel 
des  organischen  Geschehens."  1904.  [A  modernized 
Lamar  ckism.] 

**Semper,  Karl. — "The  Natural  Conditions  of  Existence  as 
they  affect  Animal  Life."  1881.  [One  of  the  finest  and 
soundest  of  biological  books,  with  an  educative  sceptical 
reserve,  discussing  in  particular  the  influence  of  the  en- 
vironment, but  before  the  question  of  the  transmission  of 
somatic  modifications  had  become  urgent.] 

Seward,  A.  C.  (Editor). — "Darwdn  and  Modern  Science." 
1909.  [A  valuable  series  of  essays  by  representative 
biologists.] 

***Spencer,  Herbert. — "Principles  of  Biology."  2  vols., 
London,  1866-68.  Revised  Edition,  1908.  [This  was,  in 
its  time,  a  masterpiece,  a  magnificent  "materialism,"  an 
incomparably  acute  analysis  and  re-synthesis  of  the 
biology  of  the  day.  The  re-edition  w^as,  in  our  judgment, 
less  valuable,  because  it  did  not  really  assimilate  the 
progress  that  had  been  made.] 


BIBLIOGRAPHY  ^55 

Sterne,  Carus  [Ernst  Krause]. — "Werden  und  Vcrcchen." 
3rd  Edition,  1886.  [A  remarkably  vivid  book  giving  an 
account  of  the  great  steps  in  evolution.] 

"Die  allgemeine  Weltanschauungen."  1889.  [An  in- 
teresting account  of  the  old  interpretations  of  the  cosmos.] 

« 

Sutton,  J.  Bland. — "Evolution  and  Disease."  1890.  [A 
very  suggestive  contribution  to  the  natural  history  of 
disease.  Comparison  of  pathological  and  normal  changes 
of  structure.]  See  also  "Introduction  to  General  Pathol- 
ogy."    1886. 

Thomson,  J.  Arthur. — "The  Science  ofj  Life."  _  1899.      [A 

short  general  survey  of  the  development  of  biology.] 
"The  Study  of  Animal  Life."     [See  examples  of  the  web 

of  life,   and  the  chapter  on  the  evolution  of  evolution 

theories.] 
■ "Heredity."     1909.     [An  exposition  of  the  problems  of 

heredity  and  an  estimate  of  the  various  contributions, — 

biometrical,  experimental  and  cytological;    and  with  an 

extensive  bibliography.] 
* "Darwinism  and  Human  Life."     1909.     [Six  lectures 

introductory  to  the  study  of  evolution  problems.] 

**TowER,  W.  L. — "Evolution  in  Chrysomelid  Beetles."  1906. 
[An  important  investigation  on  environmental  factors 
serving  as  stimuli  to  germinal  variations.] 

**Varigny,  H.  De.—" Experimental  Evolution."  1892.  [An 
admirable  introduction  to  the  experimental  study  of 
evolution.] 

*Vernon,  H.  M. — "Variation  in  Animals  and  Plants."  1903. 
[A  useful  introduction  to  the  study  of  variation  and  espe- 
cially to  the  biometric  point  of  view.] 

**Vries,  H.  De. — "Species  and  Varieties,  their  Origin  by 
Mutation."  1905.  [A  vivid  series  of  lectures  expounding 
the  author's  mutation  theory.] 

** "The  Mutation  Theory."     Translation.     2  vols.,  1910 

and  1911.  [A  detailed  account  of  the  author's  remark- 
able experiments  and  observations  on  the  origin  of  species 
in  the  vegetable  kingdom.] 

Walker,  C.  E. — "Hereditary  Characters  and  their  Modes  of 
Transmission."  1910.  [A  very  interesting  endeavour  to 
harmonize  the  results  of  the  Mendelian  experiments  with 
the  observations  of  the  biometricians.] 

♦Wallace,  Alfred  Russel. — "Darwinism."  1889.  [A 
standard  book  of  great  value  and  interest,  e.g.  in  showing 
how  the  author's  position  differs  in  certain  respects  from 
Darwin's.] 

*** "Contributions  to  the  Theory  of  Natural  Selection." 

1871. 


256  BIBLIOGRAPHY 

*Weism ANN,"  August. — "The  Evolution  Theory."  2  vols., 
1904.  [Expressing  the  final  convictions  of  a  veteran 
evolutionist,  with  a  wealth  of  fact-illustration,  which 
remain,  whatever  be  the  verdict  as  to  theory.] 

** "The    Germ-plasm."      Contemporary    Science    Series. 

1893. 

** ' '  Essays  on  Heredity  and  Kindred  Sub j  ects . "    189 1-92. 

Wilson,  E.  B. — "The  Cell  in  Development  and  in  Inherit- 
ance." 2nd  Edition,  1900.  [An  indispensable  book 
characterized  by  its  high  standard  of  accuracy  and  by 
its  maturity  of  judgment.] 


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Nor^^caronna  state  university  Ub^ries 

EVOLUTION 


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